Free science, lab and veterinary tools

243 free calculators and utilities by Dr. Zubair Khalid, DVM, MS, PhD. They run in your browser.

Statistics

• Standard Deviation Calculator – Sample and population standard deviation, variance, SEM, coefficient of variation, quartiles and skewness from raw data, with every step of the calculation shown.
• Mean, Median & Mode Calculator – Find the mean, median and mode of any data set instantly, with range, quartiles, standard deviation and the sorted list alongside.
• Variance Calculator – Sample and population variance with standard deviation, standard error and the sum-of-squares steps, from any pasted data set.
• Z-Score Calculator – Convert a raw score to a z-score and percentile, go from z back to a raw score, or standardise a whole data set with z-scores and percentiles for every value.
• P-Value Calculator – Exact p-values from z, t, chi-square and F statistics, left-, right- or two-tailed, with the critical value for your significance level.
• Confidence Interval Calculator – 95 % (or any level) confidence interval for a mean from raw data or summary statistics using t or z, and for a proportion using the Wilson score and Wald methods.
• T-Test Calculator – One-sample, independent two-sample (Welch or pooled) and paired t-tests from raw data or summary statistics, with t, df, p, the 95 % CI of the difference and Cohen's d.
• Chi-Square Test Calculator – Chi-square test of independence for any r × c contingency table with expected counts, Cramér's V and Fisher's exact test for 2 × 2, plus chi-square goodness of fit.
• Correlation Coefficient Calculator – Pearson r and Spearman ρ between two variables with p-values, r², a 95 % confidence interval for r and a plain-language interpretation of strength and direction.
• Linear Regression Calculator – Least-squares line y = a + bx with standard errors, t and p for the slope, r², F, residual standard error and prediction at any x.
• Normal Distribution Calculator – Probabilities under any normal curve — below, above, between or outside given values — and the inverse: the value at a given percentile, with z-scores.
• Probability Calculator – Binomial and Poisson probabilities, combinations and permutations, and probabilities of combined events (union, intersection, conditional and independence checks).
• Binomial Distribution Calculator – Exact binomial probability P(X = k) plus cumulative P(X ≤ k), P(X ≥ k) and tails, with mean, variance and SD for n trials at probability p.
• Poisson Distribution Calculator – Poisson probability P(X = k) for a rate λ with cumulative and tail probabilities — for counts of rare events such as colonies, mutations, reads or arrivals.
• Sample Size & Power Calculator – Sample size to compare two means or two proportions at a chosen power, survey sample size for a margin of error with finite-population correction, and the power achieved by an existing n.
• Significant Figures Calculator (Sig Fig Counter and Rounder) – Sig fig calculator: count the significant figures in any number, round to a chosen number of significant figures and convert to scientific notation, with each digit marked significant or not and the rules explained.
• ANOVA Calculator – Free one-way ANOVA calculator. Paste groups to get SS, df, MS, F and p, eta squared, Tukey HSD pairwise p-values and Welch's ANOVA for unequal variances.
• Mann-Whitney U Test Calculator – Mann-Whitney U test calculator with U, z, exact or tie-corrected p-value and effect size r. Switch to paired data for the Wilcoxon signed-rank test.
• Outlier Calculator – Find outliers with Grubbs' test (G, critical value, p), 1.5 and 3 × IQR fences, z-scores and MAD-based modified z-scores. Flagged values are highlighted.
• Coefficient of Variation Calculator – Calculate the coefficient of variation (CV%) for one or more groups using the sample SD, plus mean intra-assay CV and inter-assay CV across runs or plates.
• Odds Ratio Calculator – Odds ratio and relative risk calculator for 2 × 2 tables with 95% CIs, risk difference, number needed to treat or harm, chi-square and Fisher p.
• Sensitivity and Specificity Calculator – Calculate sensitivity, specificity, PPV, NPV, accuracy and likelihood ratios with 95% CIs from a 2 × 2 table. Add a prevalence to recompute PPV and NPV.
• False Discovery Rate and Bonferroni Correction Calculator – Paste a list of p-values to get Benjamini-Hochberg false discovery rate (FDR) adjusted p-values (q-values), Benjamini-Yekutieli, Holm and Bonferroni adjustments, the number of significant tests under each, and a table you can paste back into a spreadsheet.
• Weighted Average Calculator – Calculate a weighted average (weighted mean) from a list of values and their weights, for course grades by category weight, GPA by credit hours, average price by quantity or any other weighted data, alongside the simple average.
• Bayes' Theorem Calculator – Apply Bayes' theorem to update a probability with new evidence: compute P(A|B) from P(A), P(B|A) and P(B|not A), or the chance that a positive or negative screening test is right from prevalence, sensitivity and specificity, explained with natural frequencies.
• Empirical Rule Calculator (68-95-99.7) – Apply the empirical rule (68-95-99.7 rule) to a normal distribution: enter the mean and standard deviation to get the ranges within one, two and three standard deviations, see them on a bell curve, and find the exact percentage between any two values.
• p-hat Calculator (Sample Proportion) – Calculate the sample proportion p-hat from the number of successes and the sample size, with q-hat, the standard error, the margin of error at any confidence level, Wald and Wilson confidence intervals and a check of the success-failure condition.
• Relative Frequency Calculator – Build a relative frequency table from a list of observations or from category counts: frequency, relative frequency as a decimal and percent, and cumulative relative frequency, with a bar chart.
• Degrees of Freedom Calculator – Find the degrees of freedom for common statistical tests: one-sample and paired t-tests, two-sample t-tests with pooled variance or the Welch-Satterthwaite formula, chi-square goodness of fit and independence, one-way ANOVA, linear regression and Pearson correlation.
• Combination Calculator (nCr and nPr) – Calculate combinations (n choose r), permutations, combinations with repetition and permutations with repetition, using exact integer arithmetic so even very large results such as lottery odds are correct.
• Percentile Calculator – Find the value at a given percentile of a data set with linear interpolation (Excel PERCENTILE.INC) or the nearest-rank method, the percentile rank of a score, and the 10th, 25th, 50th, 75th and 90th percentiles.
• Interquartile Range Calculator (IQR) – Calculate the interquartile range of a data set with the first quartile, median and third quartile by the textbook median-of-halves method or Excel's QUARTILE.INC, plus the lower and upper fences and any outliers.
• Power Analysis Calculator (Sample Size for t-Tests) – Run an a priori power analysis for two-sample, paired or one-sample t-tests: find the sample size needed for a given effect size (Cohen's d), significance level and power, or the power of a study with a fixed sample size. Results match G*Power to within one subject.
• Effect Size Calculator (Cohen's d and Hedges' g) – Calculate the standardised mean difference between two groups as Cohen's d and bias-corrected Hedges' g from means, standard deviations and sample sizes or from an independent-samples t statistic, with a 95% confidence interval, the equivalent correlation r and Cohen's small/medium/large label.
• Fisher's Exact Test Calculator (2×2) – Run Fisher's exact test on a 2×2 table of counts to test the association between two categorical variables, with exact two-sided and one-sided p-values (matching R's fisher.test) and the sample odds ratio. Ideal when expected counts are too small for chi-square.

Pet Care

• Pet Health & Vaccination Record – Build a complete vaccination, weight and medication record for your dog or cat. Next booster dates are calculated automatically, and the whole record prints on one page for your vet.
• Dog Age Calculator – Estimate a dog's human-equivalent age by size and compare it with a published Labrador DNA-methylation research model.
• Cat Food & Daily Calorie Calculator – Calculate exact daily calories (RER/DER), wet canned vs. dry kibble feeding portions, hydration needs, and safe weight loss targets for cats.
• Cat Age & Human Years Calculator – Convert your cat's age to human years using peer-reviewed AAFP / AAHA guidelines, with breed-specific longevity data and clinical life-stage screening recommendations.
• Cat Pregnancy & Queening Calculator – Calculate your cat's expected queening due date, fetal development milestones, diagnostic windows (ultrasound, radiography), nutrition schedule, and labor dystocia red flags.
• Dog Calories Calculator – Daily calories for your dog from body weight and activity level, using the RER × life-stage factor method, with cups of food per day.
• Puppy Food Calculator – Determine how much to feed a growing puppy based on age, weight, and food density.
• Pet Calorie Calculator – Calculate daily calorie requirements (RER & MER) for dogs and cats for proper nutrition and weight management.
• Raw Dog Food Calculator – Determine the exact ratio of muscle meat, bone, and secreting organs needed for your dog's raw diet.
• Freeze Dried Dog Food Calculator – Calculate daily patty/nugget portions and rehydration water volume for freeze-dried pet food.
• Aquarium Volume & Medication Dose Calculator – Work out how many gallons are really in your tank after substrate and decor, then scale any medication label dose and water change to that volume.
• Aquarium Fish Stocking Calculator – Check whether your tank is overstocked: enter tank size and the fish you keep (or plan to) to see the bioload against the tank's capacity.
• Aquarium Substrate Calculator – Calculate substrate weight (lbs/kg) needed for sand, gravel, or aquasoil beds.
• Dog Water Intake Calculator – How much water your dog needs per day by weight and diet, in mL and cups, and the intake that counts as excessive thirst (over 100 mL/kg/day).
• Dog Feeding Calculator & Daily Food Portion Planner – Calculate your dog's exact daily caloric needs (RER & DER), dry kibble cups and grams, canned wet food portions, and safe treat limits using NRC and WSAVA clinical standards.
• Dog Pregnancy Calculator & Canine Whelping Due Date Calendar – Work out your dog's due date from the breeding or ovulation date, with the week-by-week pregnancy timeline, ultrasound and X-ray windows and signs labor is near.
• Kitten Weight Calculator & Growth Milestone Chart – Track neonatal kitten weight gain (7–10g/day), evaluate growth percentiles (0–24 weeks), calculate orphan Kitten Milk Replacer (KMR) volumes, and monitor developmental milestones and hypothermia alerts.
• Dog Crate Size Calculator & Bedding Dimensions Guide – Calculate the exact ergonomic crate size, internal dimensions, commercial crate match, and IATA airline travel container specs for your dog based on nose-to-tail length and standing height.
• Puppy Vaccination Schedule Calculator – Enter your puppy's date of birth to get a dated vaccination schedule following the 2022 AAHA Canine Vaccination Guidelines: core DAPP (distemper, adenovirus, parvovirus, parainfluenza) every 3 weeks until 16 weeks or older, rabies, leptospirosis, and optional Bordetella, Lyme and canine influenza vaccines, with the next shot due and adult boosters.
• Hamster Age Calculator (Hamster Years to Human Years) – Convert your hamster's age in months to human years based on how far through its species' typical lifespan it is, with life stage and lifespan for Syrian, Roborovski, winter white, Campbell's dwarf and Chinese hamsters, plus an age chart.
• Dog Heat Cycle Calculator – Track a female dog's heat (estrous) cycle from the first day of bleeding: see the current phase (proestrus, estrus, diestrus), the likely fertile window for breeding, when the heat should end and the expected dates of her next three heats based on her size or own cycle length.
• Cat Color Genetics Calculator (Kitten Colors) – Predict the colours of a litter of kittens from the mother's and father's coat colours. The calculator follows the X-linked orange gene and the recessive dilute gene to give the chance of black, blue (grey), red (orange), cream, tortoiseshell and blue-cream kittens, separately for males and females.

Health & Wellness

• BMI Calculator & Medical Ideal Body Weight (IBW) Planner – Calculate Body Mass Index (BMI) using WHO/CDC criteria and evaluate clinical Ideal Body Weight (IBW) using Devine, Robinson, and Hamwi formulas, plus Adjusted Body Weight (ABW) and healthy weight targets.
• Body Fat Percentage Calculator & Lean Mass Index – Calculate your body fat percentage, lean body mass (LBM), and fat mass using the US Navy tape method or 3-site caliper skinfold equation, with ACE category classifications and target fat loss planning.
• Body Surface Area (BSA) Calculator – Calculate human and veterinary body surface area in square meters (m²) using Mosteller, DuBois, Haycock, and Gehan-George formulas for clinical chemotherapy dosing and renal indexing.
• Calorie Deficit Calculator & Target Goal Date Planner – Calculate your daily calorie deficit, target goal completion date, and macronutrient preservation targets based on the 3,500 kcal fat rule, metabolic adaptation buffers, and safe weekly loss limits.
• Ovulation Calculator & Period Tracker – Estimate your ovulation date, fertile window and next period from the first day of your last period and your average cycle length, with the next six cycles laid out and the due date if you conceive this cycle.
• One Rep Max Calculator (1RM) – Estimate your one rep max (1RM) for bench press, squat, deadlift or any lift from the weight and reps of a hard set, averaged across the Epley, Brzycki, Lombardi, Lander, Mayhew and Wathan formulas, with a table of training weights from 60% to 100% of 1RM.
• BMR Calculator (Basal Metabolic Rate) – Calculate your basal metabolic rate with the Mifflin-St Jeor equation, compare it with the revised Harris-Benedict and Katch-McArdle (lean mass) equations, and see total daily energy expenditure for every activity level.
• Blood Alcohol Calculator (BAC) – Estimate your blood alcohol content (BAC) from the drinks you had, body weight, sex and hours since your first drink using the Widmark formula, and see roughly how long until your BAC returns to zero.
• Sleep Calculator (Bedtime and Wake-Up Times) – Enter when you need to wake up to see the best bedtimes, or enter when you're going to bed to see the best wake-up times, based on 90-minute sleep cycles and the time it takes to fall asleep.
• Pace Calculator (Running Pace, Time and Distance) – Calculate running or walking pace per kilometre or mile from distance and time, find finish time from a target pace, or work out distance, with race presets and speed in km/h and mph.
• eGFR Calculator (CKD-EPI 2021) – Estimate kidney function (eGFR) with the 2021 race-free CKD-EPI creatinine equation recommended by the NKF and ASN, using serum creatinine in mg/dL or µmol/L, age and sex, and see the KDIGO GFR category.
• Protein Intake Calculator – Work out how much protein you need each day from your body weight and goal, from the RDA minimum to muscle gain, fat loss, endurance training, older age and pregnancy, with grams per meal and common food sources.
• MELD Score Calculator (MELD, MELD-Na, MELD 3.0) – Calculate the Model for End-Stage Liver Disease score in three versions: original MELD, MELD-Na and MELD 3.0 (used by OPTN for US liver allocation since 2023), with estimated 90-day mortality.
• Heart Rate Zone Calculator – Calculate your five heart rate training zones with the Karvonen heart rate reserve method or percentage of maximum heart rate, using the Tanaka (208 − 0.7 × age) or 220 − age formula, or your own measured max.
• Caffeine Calculator – Total your daily caffeine from coffee, espresso, tea, cola, energy drinks and pre-workout, compare it with FDA, ACOG and pediatric limits, and estimate how much caffeine is still in your system hours later using a 5-hour half-life.
• Mean Arterial Pressure Calculator (MAP) – Calculate mean arterial pressure from systolic and diastolic blood pressure with the standard formula MAP = DBP + (SBP − DBP)/3, plus pulse pressure and how the result compares with the normal 70–100 mmHg range and the 65 mmHg target used in shock.
• Pack Years Calculator – Calculate smoking pack-years from cigarettes or packs per day and years smoked, including several smoking periods, and check eligibility for lung cancer screening under the 2021 USPSTF guideline (age 50–80, 20 pack-years).

Chemistry

• Molecular Weight Calculator – Molar mass of any chemical formula from IUPAC atomic weights, with element-by-element breakdown, percent composition and a mass-to-molarity converter. Handles brackets, hydrates and ions.
• Osmolarity Calculator – Osmolarity of a lab solution from its solutes (mM, g/L or %) using dissociation factors, and serum osmolality from sodium, glucose and BUN with the osmolal gap.
• Moles to Grams Calculator – Convert grams to moles, moles to grams and moles to molecules. Type a formula like CuSO4·5H2O and the molar mass is worked out from IUPAC atomic weights.
• PPM Calculator – Convert ppm to mg/L, ppb, µg/mL, percent and molarity for water-based solutions, and find how much solute to weigh for a target ppm and volume.
• Percent Yield Calculator – Enter reactant masses and the balanced equation coefficients to find the limiting reagent, theoretical yield and percent yield, with excess left over.
• Molarity Calculator – Calculate the mass to weigh for a solution of a given molarity and volume, or solve for molarity or volume, from the molecular weight. Units from M to nM, L to µL, g to µg.
• Electron Configuration Calculator – Find the electron configuration of any element from hydrogen to oganesson, or of an ion such as Fe²⁺ or Cl⁻, with the noble gas shorthand, an orbital box diagram, electrons per shell, valence electrons and the number of unpaired electrons. Known exceptions such as chromium and copper are handled.
• Arrhenius Equation Calculator – Solve the Arrhenius equation k = A·e^(−Ea/RT): find the rate constant at a temperature, the activation energy from rate constants at two temperatures, or how much a reaction speeds up when it is heated, with °C or kelvin input.
• Average Atomic Mass Calculator – Calculate the average atomic mass of an element from the mass and natural abundance of each isotope, with presets for chlorine, copper, magnesium and boron, and work backwards to find the percent abundance of two isotopes from a known average.
• Density Calculator – Calculate density from mass and volume, or find mass or volume from density, with unit conversion between grams, kilograms, pounds, millilitres, litres, cubic metres, cubic feet and gallons, and reference densities for water, metals and everyday materials.
• Ideal Gas Law Calculator (PV = nRT) – Solve the ideal gas law for pressure, volume, amount of gas or temperature, with pressure in atm, kPa, Pa, bar, mmHg, torr or psi, volume in L, mL, m³ or ft³, and temperature in °C or kelvin.
• pH Calculator – Calculate the pH of a solution from hydrogen ion concentration, a strong acid or base, or a weak acid or base with its Ka or Kb (solved exactly with the quadratic), and convert between pH, pOH, [H⁺] and [OH⁻].
• Stoichiometry Calculator (Limiting Reagent and Theoretical Yield) – Work through stoichiometry from a balanced chemical equation: convert grams of reactant to grams of product, find the limiting reagent between two reactants, the theoretical yield and how much excess reagent is left, with molar masses calculated from formulas.
• Empirical Formula Calculator – Find the empirical formula of a compound from its percent composition or the mass of each element, showing moles, mole ratios and the multiplier used, and the molecular formula when the molar mass is known.
• Mass Percent Calculator (Percent Composition) – Calculate the percent composition by mass of each element in a chemical formula, with molar mass, or the mass percent (w/w) concentration of a solute in a solution from the masses of solute and solvent.

Research & Writing

• Citation Checker – Check citations free. Paste your reference list and each entry is matched against Crossref, PubMed, OpenAlex, Europe PMC, Semantic Scholar, DataCite and Open Library to catch fake, invented, retracted or wrong references, then fix and reformat the list in any citation style.
• Literature Review Generator – Free literature review generator. Find papers on any topic, get an evidence table, a citation map, a cited review draft, and Excel, BibTeX or RIS files.
• Generate Citation from DOIs – Paste DOIs and get formatted references for any journal. 10,800+ styles including APA, Vancouver, AMA, Nature, Cell, PLOS ONE and BibTeX. Free, no sign-up.
• AMA Citation Generator – Paste DOIs and get AMA references built from Crossref and PubMed records. Switch to 10,800+ journal styles. Free.
• APA Citation Generator – Paste DOIs and get references formatted in APA Style, 7th edition. Built from Crossref and PubMed records. Switch to any of 10,800+ journal styles. Free.
• MLA Citation Generator – Paste DOIs and get MLA references built from Crossref and PubMed records. Switch to 10,800+ journal styles. Free.
• Chicago Citation Generator – Paste DOIs and get Chicago references built from Crossref and PubMed records. Switch to 10,800+ journal styles. Free.
• IEEE Citation Generator – Paste DOIs and get references formatted in IEEE Reference Guide. Built from Crossref and PubMed records. Switch to any of 10,800+ journal styles. Free.
• Harvard Reference Generator – Paste DOIs and get Harvard references built from Crossref and PubMed records. Switch to 10,800+ journal styles. Free.
• Vancouver Citation Generator – Paste DOIs and get Vancouver references built from Crossref and PubMed records. Switch to 10,800+ journal styles. Free.
• ACS Citation Generator – Paste DOIs and get ACS references built from Crossref and PubMed records. Switch to 10,800+ journal styles. Free.
• Nature Citation Style Generator – Paste DOIs and get references formatted in Nature journal style. Built from Crossref and PubMed records. Switch to any of 10,800+ journal styles. Free.
• DOI to BibTeX Generator – Paste DOIs and get references formatted in BibTeX. Built from Crossref and PubMed records. Switch to any of 10,800+ journal styles. Free.

Farm Planning

• Pasture Stocking Rate Calculator – Estimate how many cattle, sheep, goats, or horses a pasture can carry from acreage, forage yield, and utilization rate.
• Livestock Water Requirements Calculator – Daily and weekly drinking-water needs for cattle, sheep, goats, pigs, horses, and poultry flocks, with hot-weather adjustment.
• Livestock Feed Cost Calculator – Price a ration on a dry-matter basis: compare silage, hay, and grain fairly and see cost per head per day and herd cost.
• Poultry Flock Feed Calculator – Project total feed for a broiler grow-out or daily feed and feed-per-dozen-eggs for a layer flock, using FCR and rate of lay.
• Horse Weight Calculator & Equine Dewormer Tape Dosage – Calculate equine body weight using heart girth and body length tape measurements with age-adjusted divisors, and determine exact clinical doses for ivermectin, fenbendazole, Banamine, and daily forage hay requirements.
• Cow Gestation Calculator (Calving Date) – Work out a cow's calving date from the breeding or AI date, with breed averages (Angus, Hereford, Holstein, Jersey, Brahman, Charolais, Simmental) and the normal window. Also sheep, goat, pig, horse, alpaca and rabbit.
• Egg Incubation Calculator (Hatch Date) – Enter the day eggs went into the incubator to get the expected hatch date and window, candling days, the stop-turning (lockdown) day and today's day count, with forced-air temperature and wet-bulb humidity for 11 poultry species.
• Chicken Coop Size Calculator – How big a chicken coop and run you need for bantams, standard hens or heavy breeds, free-range or confined, plus roost length, nest boxes and feeder and waterer space, using Virginia, NC State and eXtension figures.
• Flock Egg Production Calculator – Estimate how many eggs a backyard flock will lay per week, month and year from the number of hens, breed type (high-production layer, heritage dual-purpose, Khaki Campbell ducks), hen age, daylight and molt, using extension figures.
• Pig Weight Calculator (Heart Girth Tape) – Estimate a pig's live weight without a scale using heart girth x heart girth x body length ÷ 400 (inches to pounds), with metric conversion, the small-pig correction, a rough carcass weight and days to your target market weight from average daily gain.
• Backyard Egg Cost Calculator – Work out the cost per egg and per dozen from a backyard flock: flock size, feed price and bag size, feed per hen per day, eggs per hen per week, other monthly costs and the coop and startup costs amortized over several years.
• Grain Bin Calculator (Bushels and Tons) – Estimate grain bin capacity and inventory: bushels in a round bin from its diameter and grain depth, including the cone of a peaked top at the grain's angle of repose or a measured peak height, converted to tons with standard test weights and to dollars at your price.

Home & Garden

• Concrete Calculator (Slabs, Footings, Columns, Steps) – Work out how much concrete you need for a slab, patio, footing, wall, round column, post hole or steps, in cubic yards, cubic metres and the number of 40, 60 and 80 lb premix bags, with a waste allowance and an optional ready-mix cost.
• Square Footage Calculator (Rooms, Floors, Lots) – Calculate the square footage of a room, floor, house, yard or lot. Add as many rectangles, triangles and circles as you need for L-shaped or irregular spaces, add a waste allowance, and get square feet, square metres, square yards and the cost at a price per square foot.
• Gravel Calculator (Tons and Cubic Yards) – Work out how much gravel you need for a driveway, path, patio base or garden bed in tons, cubic yards, cubic metres and 0.5 ft³ bags, for gravel, pea gravel, crushed stone, river rock, sand, road base or topsoil, with an optional cost.
• Mulch Calculator (Cubic Yards and Bags) – Find how much mulch, bark, wood chips, compost or soil you need for a garden bed, border or tree ring in cubic yards, cubic metres and 2 ft³ or 3 ft³ bags, with an optional bulk cost.
• Soil Calculator (Cubic Yards and Bags) – Calculate how much soil you need for raised beds, garden beds or lawn topdressing: cubic yards for bulk delivery, cubic feet, number of bags, and approximate weight for topsoil, garden soil, potting mix or fill dirt, with an allowance for settling.
• Grass Seed Calculator – Work out how much grass seed to buy for a new lawn or for overseeding, using extension seeding rates for Kentucky bluegrass, tall fescue, perennial ryegrass, fine fescue, bermuda, zoysia, centipede, bahia and buffalograss, in pounds, kilograms and bags.
• Compost Calculator (How Much to Spread and C:N Ratio) – Two compost calculators in one: work out how much compost to spread on beds or a lawn in cubic yards, cubic feet and bags; or mix greens and browns and see your pile's carbon-to-nitrogen (C:N) ratio calculated on a dry-weight basis, with advice to reach the ideal 25–30:1.
• Fertilizer Calculator (NPK) – Calculate how much fertilizer product to spread on a lawn or garden from its N-P-K analysis and a target rate of nitrogen, phosphate or potash per 1,000 square feet, with total pounds, bags and the nutrients you will actually apply.
• Plant Spacing Calculator – Calculate how many plants, seedlings or ground-cover plugs you need for a garden bed from its size and the plant spacing, with square-grid, triangular (offset) and row layouts and the choice of starting half a space in from the edge.

Veterinary

• Chocolate Toxicity Calculator – Enter your dog's weight, the chocolate type and how much was eaten to see the theobromine dose in mg/kg, the risk level and when to call a vet or poison line.
• Dog Weight Loss Calculator – Set a healthy weight loss caloric target and feeding amount for overweight dogs.
• Dog IV Fluid Rate Calculator – Clinical tool calculating maintenance, dehydration deficit, and IV drip rates (drops/min).
• Dog Pregnancy / Whelping Calculator – Calculate your dog's expected whelping date and key pregnancy milestones based on mating date.
• Feline Grimace Scale Calculator – Score a cat's acute pain with the Feline Grimace Scale: ear position, orbital tightening, muzzle tension, whiskers and head position, 0–2 each. A score of 4/10 or more (ratio 0.39) means analgesia is recommended.
• Anion Gap Calculator – Calculate the anion gap from Na⁺, Cl⁻ and HCO₃⁻ (with K⁺ for dogs and cats), correct it for low albumin, and compare with human, dog or cat reference ranges.
• Corrected Calcium Calculator – Correct total serum calcium for low or high albumin with the Payne formula, in US (mg/dL) or SI (mmol/L) units, and compare with the normal range.
• IRIS CKD Staging Calculator (Cats & Dogs) – IRIS chronic kidney disease stage for cats and dogs from blood creatinine (mg/dL or µmol/L) and SDMA, with proteinuria (UPC) and blood-pressure substages, using the 2023 IRIS cut-offs.

Developer Utilities

• Text & Code Diff Checker – Compare two text, markdown, or code snippets side-by-side to visually inspect line-by-line additions, deletions, and character modifications.
• JSON Formatter, Validator & Minifier – Format messy JSON with 2-space or 4-space indentation, validate syntax with exact error line pointers, and minify JSON for production.
• Case Converter & Text String Formatter – Transform text between Title Case, Sentence case, UPPERCASE, lowercase, camelCase, PascalCase, snake_case, and kebab-case.
• Base64 String Encoder & Decoder – Encode UTF-8 text strings to Base64 and decode Base64 strings to plain text completely client-side in your browser.
• QR Code Generator & Creator – Create scannable, high-resolution QR codes for website URLs, plain text, and Wi-Fi login access with downloadable PNG and SVG images.
• Secure Password Generator – Generate cryptographically secure, random passwords locally in your browser with custom length and character rules.
• Unix Epoch Timestamp Converter – Instantly convert Unix timestamps (seconds or milliseconds) to human-readable dates and local times.
• Color Code Converter (HEX to RGB) – Convert CSS color codes between HEX and RGB formats with an instant visual swatch preview.

Molecular Biology

• Codon Table (Interactive Genetic Code) – Interactive standard genetic code with all 64 codons, RNA/DNA toggle, search by amino acid or codon, synonymous codons and amino-acid properties on click.
• Amino Acid Chart – All 20 standard amino acids with one- and three-letter codes, molecular weight, side-chain pKa, pI, Kyte–Doolittle hydropathy, class, polarity, charge, essentiality and codons — sortable, searchable and exportable.
• qPCR Efficiency & Standard Curve Calculator (Copy Number) – Paste a qPCR dilution series to get slope, R² and amplification efficiency, convert sample Cq values to copy number, and calculate copies/µL for plasmid standards.
• ΔΔCt Calculator: qPCR Fold Change and Relative Expression – Paste Ct values from Excel or your qPCR instrument, or type them in, for any number of samples, genes and replicates. Get ΔCt, ΔΔCt, fold change (2^-ΔΔCt or efficiency-corrected Pfaffl), log2 fold change, error bars, Welch t-tests with Holm correction, quality checks and a CSV.
• Ligation Insert-to-Vector Mass Calculator – Calculate the ng of insert DNA required for ligation.
• Transformation Efficiency Calculator – Calculate bacterial transformation efficiency (cfu/µg) from the number of colonies, the amount of plasmid DNA added, the recovery volume, the volume plated and any dilution, with a grade for chemically competent and electrocompetent cells.

Cell Biology

• IC50 Calculator (Dose–Response Curve Fit) – Fit a four-parameter logistic dose–response curve to your concentration–viability data and get the IC50, Hill slope, plateaus and R². Accepts % viability or raw MTT/XTT absorbance with control and blank.
• EC50 Calculator (Dose–Response Curve Fit) – Fit a four-parameter logistic agonist dose–response curve and get the EC50, Hill slope, Emax and R² from concentration–response data.
• MTT Assay Calculator: Cell Viability % and IC50 – Calculate % cell viability and cytotoxicity from raw MTT, MTS, CCK-8 or CellTiter-Glo plate readings with replicate wells, and estimate IC50 from a dose series.
• Water Potential Calculator – Calculate solute potential with Ψs = −iCRT, add pressure potential to get water potential (Ψ = Ψs + Ψp) in bars and MPa for a cell and the solution around it, see which way water moves, and get the osmotic pressure of each side.
• Microscope Magnification Calculator – Calculate total magnification from the objective and eyepiece, field of view diameter from the field number, resolution and useful magnification from the numerical aperture, the actual size of a specimen from an image and magnification, and cell size from how many cells fit across the field.

Data Visualization

• Bar Graph Maker – Free bar graph maker for lab data. Paste a table, average replicates, add SD or SEM error bars and data points, then download SVG or PNG.
• Box Plot Maker – Free box and whisker plot maker. Paste columns of values to get quartiles, median, 1.5 IQR whiskers, outliers, a five-number summary and SVG or PNG export.
• Scatter Plot Maker – Free scatter plot maker. Paste x,y data with optional groups, add a linear trendline with its equation and R squared, use log axes, download SVG or PNG.
• Volcano Plot Maker – Free online volcano plot maker. Paste gene, log2 fold change and p or adjusted p, set cutoffs, label top genes, count up and down genes, export SVG or PNG.
• Venn Diagram Maker – Free Venn diagram maker for 2 or 3 sets. Paste gene or item lists to find overlaps and unique items per region, or enter counts. Export SVG, PNG or CSV.

Genetics

• Punnett Square Calculator – Make a Punnett square for any cross with up to 3 genes. Enter parent genotypes like AaBb × AaBb to get the grid, genotype ratios and phenotype ratios.
• Horse Coat Color Calculator – Foal color odds from sire and dam: bay, chestnut, black, palomino, buckskin, cremello, perlino, dun, grullo, silver, champagne, grey, roan, tobiano, overo and appaloosa.
• Hardy-Weinberg Equilibrium Calculator – Calculate genotype frequencies from allele frequency.
• Hardy-Weinberg Calculator – Calculate allele and genotype frequencies under Hardy-Weinberg equilibrium from observed genotype counts, the frequency of a recessive trait (q²) or an allele frequency, estimate the carrier rate (2pq), and test whether a population departs from equilibrium with a chi-square test.

Molecular Assays

• PCR Master Mix & Reaction Cocktail Calculator – Calculate master mix cocktail recipes for standard and 96-well PCR reactions with automatic pipetting loss overage compensation.
• Oligo Reconstitution & Resuspension Calculator – Calculate exact volume of TE buffer or nuclease-free water to add to lyophilized primers to achieve 100 µM or custom stock concentrations.
• DNA Ligation & Insert-to-Vector Ratio Calculator – Calculate exact insert DNA mass (in ng) required for molecular cloning at 1:1, 3:1, 5:1, or custom molar ratios.
• Gibson Assembly Calculator – Calculate how much of each DNA fragment to add to a Gibson Assembly or NEBuilder HiFi reaction. Enter fragment lengths and concentrations, the vector amount and insert-to-vector molar ratio, and get pmol, ng and µL per fragment, master mix and water volumes, and a check against NEB's recommended total DNA.

Math & Finance

• Percentage & Percent Change Calculator – Calculate what is X% of Y, find percentage increase or decrease, fraction proportions, and discount markups with step-by-step mathematical steps.
• Tip Calculator (Split the Bill) – Calculate the tip and total for a restaurant bill at 15, 18, 20 or any percentage, split it between any number of people, tip on the pre-tax amount, and round each share up to the next dollar.
• Discount Calculator (Sale Price and % Off) – Find the sale price and how much you save from a percentage discount, stack an extra percent off, add sales tax, or work backward from the sale price to the percent off.
• Sales Tax Calculator – Add sales tax to a price or remove it from a total that already includes tax, using any rate or the base sales tax rate for each US state, and see tax amount, pre-tax price and total.

STEM & Mathematics

• Scientific Calculator Online – Perform advanced mathematical operations online including trigonometric functions (sin, cos, tan in deg/rad), logarithms (ln, log10), powers, factorials, and constants (pi, e).
• Fraction Calculator (Add, Subtract, Multiply, Divide) – Add, subtract, multiply, and divide proper fractions, improper fractions, and mixed numbers with step-by-step Least Common Denominator (LCD) reduction and visual fraction breakdown.
• Ratio Calculator – Free ratio calculator: solve for the missing value in a proportion A : B = C : D, simplify any ratio to lowest terms, scale a ratio up or down, and convert it to a unit ratio (1 : N or N : 1), with the cross-multiplication shown.
• Logarithm Calculator (log, ln, log2, any base) – Calculate logarithms in any base, including log base 10, natural log (ln) and log base 2, using the change-of-base formula, or find the antilog (base raised to a power).

Solution Preparation

• Serial Dilution Calculator – Plan a serial dilution: concentration, transfer volume and diluent volume for every tube. Also calculates the total dilution factor across several steps.
• Dilution Calculator (C1V1 = C2V2) – Dilution calculator using C1V1 = C2V2: enter the stock concentration, the concentration you want and the final volume to get the volume of stock to pipette, the diluent to add and the dilution factor. Works in M, mM, µM, nM, mg/mL, µg/mL and percent.
• Percent Solution Calculator – Work out how much solute to weigh or measure for a percent solution (w/v, v/v or w/w), how to dilute a stock percentage to a working percentage, and how to convert % w/v to molarity and back from the molecular weight.

Primer Design

• BatchClone – Design primers for seamless batch cloning and Gibson Assembly with interactive plasmid maps and real-time DNA design.
• Primer Tm Calculator – Paste a primer sequence to get its melting temperature (Wallace rule for short oligos, Marmur/GC formula for longer ones), GC content and length.
• PCR Primer Design Tool – Design PCR primers from a DNA template in your browser. Set product size, primer length, Tm and GC limits; the tool scans both strands, filters out runs, weak or overloaded 3′ ends and 3′ self- and cross-complementarity, and ranks primer pairs by matched Tm and product size.

Proteomics

• Online PDB Viewer: 3D Protein Structure Viewer – Open any PDB ID, a UniProt ID (AlphaFold model) or your own .pdb / .cif file and view the 3D structure in the browser: cartoon, surface and sticks, residue highlighting and pLDDT coloring. No install.
• Protein Properties – Compute MW, isoelectric point, GRAVY, extinction coefficient, and AA composition.
• Hydropathy Plot (Kyte-Doolittle) – Make a Kyte-Doolittle hydropathy plot or a Hopp-Woods hydrophilicity plot from a protein sequence, with an adjustable sliding window, GRAVY score, predicted membrane-spanning segments and a CSV of window scores.

Analysis

• Sequence Statistics – Length, GC content, base composition, and molecular weight for DNA, RNA, or protein.
• ORF Finder – Locate open reading frames across all six frames with customizable minimum length.
• Codon Usage – Tabulate codon counts and frequencies for a coding DNA sequence.

Cell Culture

• Cell Viability & Hemocytometer Counting Calculator – Calculate live cell concentration (cells/mL), Trypan blue exclusion viability percentage, and total culture yield from hemocytometer grid counts.
• Cell Doubling Time & Specific Growth Rate Calculator – Calculate population doubling time (Td), specific growth rate (µ), and generation count for mammalian and microbial cell cultures.
• Cell Seeding and Dilution Calculator – Plan cell seeding for 6- to 96-well plates, dishes and flasks: enter your counted cell concentration and a target in cells per well or cells/cm², and get the suspension volume, fresh medium, cells per well and total cells with a pipetting margin. A second mode dilutes a cell suspension to a target cells/mL with C₁V₁ = C₂V₂.

Writing & Content

• Word Counter & Text Readability Analyzer – Count words, characters, sentences, and paragraphs in real time with Flesch Reading Ease score, reading time, and speaking speed estimates.
• Markdown Table Generator & Spreadsheet Editor – Visual spreadsheet editor to create, format, align, and copy clean GitHub-flavored markdown tables for documentation and scientific manuscripts.
• Lorem Ipsum & Dummy Text Generator – Generate classic Latin placeholder paragraphs, sentences, or word counts for web design, mockups, and layout testing.

Laboratory Calculators

• Lineweaver-Burk Plot & Michaelis-Menten Calculator – Fit Michaelis-Menten kinetics from your [S] and rate data. Get Km and Vmax with standard errors, a Lineweaver-Burk plot, kcat and SVG or PNG figures.
• Peptide Calculator (Reconstitution and Syringe Units) – Peptide reconstitution calculator: from the vial size in mg and the bacteriostatic water added in mL, get the concentration (mg/mL and mcg per unit), the volume to draw for a given amount in mcg or mg, the units on a U-100 or U-40 insulin syringe, and how many equal draws the vial holds. It does the arithmetic only and does not choose a compound or dose.

Alignment

• OmniAlign Studio – Compare variant sequences against a reference (or each other) and instantly extract mutations. Protein and nucleotide modes.
• Pairwise Alignment – Global Needleman-Wunsch alignment with score, identity, and gap statistics.

Manipulation

• Reverse Complement – Generate the reverse, complement, and reverse-complement strands of any DNA sequence.
• Transcribe DNA → RNA – Convert a DNA coding strand to its corresponding mRNA sequence.

Utilities

• FASTA Parser – Parse multi-record FASTA input, inspect each entry, and re-export cleanly formatted.
• Random DNA Generator – Generate random DNA sequences of any length with a target GC content, for testing primers, pipelines and teaching.

Virology

• Viral Plaque Assay (PFU/mL) & MOI Calculator – Calculate virus titer in PFU/mL from plaque counts, dilution and inoculum volume, then the virus volume needed for a target MOI. Shows the working for each step.
• TCID50 Viral Titer (Reed & Muench) Calculator – Calculate 50% Tissue Culture Infectious Dose (TCID50/mL) and equivalent PFU/mL using the Reed-Muench mathematical endpoint method.

Math & Science

• Universal Unit & Metric Converter – Instant two-way conversion for length, mass, temperature, volume, velocity, and digital data storage with exact scientific formulas.
• Scientific Notation & Significant Figures Calculator – Convert decimal numbers to scientific notation ($a \times 10^b$) and engineering notation, and count exact significant figures (sig figs).

Laboratory Tools

• Radioactive Decay Calculator – Calculate the remaining quantity of a radioactive substance based on initial amount, half-life, and elapsed time.
• Chemical Equation Balancer – Automatically balance complex chemical equations and stoichiometry matrices using Gaussian elimination.

Time & Scheduling

• Date Calculator & Business Days Duration – Calculate exact days between two calendar dates, count business working days (excluding weekends and statutory holidays), or add/subtract days from any starting date.
• Chronological Age Calculator (Years, Months, Days) – Determine your exact chronological age in years, months, and days from your date of birth, with total elapsed hours, minutes, seconds, and an upcoming birthday countdown.

Physiology & Health

• Daily Water Intake Calculator & Hydration Target – Calculate your optimal daily fluid intake in ounces, liters, and 8-oz glasses based on body mass, exercise duration, climate, and metabolic factors.
• Creatinine Clearance Calculator (Cockcroft-Gault) – Estimate creatinine clearance (CrCl) with the Cockcroft-Gault equation from age, sex, weight, height and serum creatinine in mg/dL or µmol/L. Shows CrCl with actual, ideal (Devine) and adjusted body weight and picks the weight usually recommended for renal drug dosing.

Ecology

• Population Growth Calculator – Calculate population size with exponential (N₀e^rt), logistic (carrying capacity K) or discrete (λ) growth models, or work out the intrinsic growth rate r from two counts, with doubling time and a growth curve.
• Shannon and Simpson Diversity Index Calculator – Paste species counts to get the Shannon diversity index (H′ in natural log and bits), Simpson's index D, Simpson's index of diversity 1 − D, the reciprocal 1/D, Pielou's evenness, effective number of species, Berger-Parker dominance and Margalef and Menhinick richness, with a step-by-step table.

Translation

• Six-Frame Translation – Translate DNA into protein across all six reading frames using the standard genetic code.

Cloning

• Restriction Site Finder – Scan a DNA sequence for common Type II restriction enzyme recognition sites.

Comparison

• Hamming Distance – Position-wise mismatches and percent identity for two equal-length sequences.

Microbiology

• CFU Calculator: Colony Forming Units per mL (CFU/mL) – Calculate CFU/mL or CFU/g from replicate plate counts across one or two dilutions, with automatic 30-300 plate selection, FDA BAM weighted averaging, and a transformation efficiency mode.

Veterinary Toxicology

• Pet Poisoning Calculator: Chocolate, Xylitol, Grapes & Medicines – Estimate how serious a dog or cat's ingestion is (mg/kg) for chocolate, xylitol, grapes and raisins, acetaminophen, ibuprofen and naproxen, with clear next steps and poison hotline numbers.

Veterinary Medicine

• Veterinary Fluid & RER Calculator – Calculate daily Resting Energy Requirements (RER) and comprehensive IV fluid therapy rates (maintenance + dehydration deficit + ongoing losses) for animal patients.

Veterinary Pharmacology

• Veterinary Liquid Medication & Dosage Calculator – Convert mg/kg prescription dosages to exact liquid mL volumes, daily administration totals, course volumes, and syringe graduation sizing.

Laboratory Chemistry

• Solution Dilution Calculator (C₁V₁ = C₂V₂) – Calculate stock solution volume needed to prepare a target working concentration using the conservation of mass equation C1V1 = C2V2.

Livestock Production

• Livestock FCR & ADG Production Calculator – Calculate Feed Conversion Ratio (FCR) and Average Daily Gain (ADG) for beef, dairy, swine, and poultry.

Laboratory Equipment

• Centrifuge RCF (g-force) ↔ RPM Converter – Convert between Relative Centrifugal Force (RCF in × g) and Rotational Speed (RPM) based on centrifuge rotor radius.

Microbiology & Fermentation

• OD600 to Cell Density & Biomass Converter – Convert spectrophotometric OD600 optical density measurements to cell counts (cells/mL) and dry cell biomass (g/L DCW) for E. coli and yeast.

Spectrophotometry

• Protein & DNA Concentration Calculator (BCA, Bradford, A260) – Calculate protein concentration from a BCA, Bradford or Lowry standard curve, DNA/RNA concentration and purity from A260/A280/A230, or any concentration from A = εcl.

Buffer Chemistry

• Buffer Preparation & Henderson-Hasselbalch Calculator – Calculate weak acid and conjugate base masses required to prepare biological buffers at target pH using the Henderson-Hasselbalch equation.

Electrophoresis

• Gel Recipe Calculator: Agarose, SDS-PAGE & Native PAGE – Get the agarose mass, buffer dilution and stain volume for an agarose gel, or full resolving and stacking gel recipes for SDS-PAGE and native PAGE at 6-15%.

Time Management

• Pomodoro Focus Timer & Task Tracker – Boost scientific productivity and deep work with customizable 25-minute focus intervals, short breaks, audio notifications, and daily session tracking.

Academic & Education

• College & High School GPA Calculator – Calculate cumulative semester GPA with standard 4.0 or 4.33 scales, weighted AP/Honors course credits, and letter grade conversion.

SEO & Web Tools

• URL Slug & Clean Permalink Generator – Convert article titles, headlines, and strings into clean, SEO-optimized URL permalinks with custom separators and stop-word filtering.

Design & Media

• Aspect Ratio & Screen Resolution Calculator – Calculate proportional width and height scaling (W1:H1 = W2:H2) with common resolution presets (16:9, 4:3, 1:1, 9:16, 4K, 1080p).

Math & Utilities

• Random Number & Decision Picker Wheel – Generate cryptographically randomized numbers within custom ranges, roll dice, flip coins, or pick winning items from a list.

Feline Health & Nutrition

• Cat Weight Calculator & Ideal Body Condition Score (BCS) – Assess your cat's body condition against the 9-point WSAVA Body Condition Score, calculate ideal target weight, resting energy requirement (RER), and safe weekly weight reduction pace.

Feline Care & Husbandry

• Cat Litter Box Calculator & Monthly Substrate Estimator – Calculate optimal litter box dimensions based on feline nose-to-tail length (AAFP standard), required substrate depth, initial fill volume, and monthly replacement costs across clumping clay, silica gel, and pine pellets.

Canine Growth & Development

• Puppy Weight Calculator & Adult Size Predictor – Predict your puppy's adult body weight, mature size category, and remaining growth trajectory using age-specific canine Gompertz growth models across toy, small, medium, large, and giant breeds.

Feline Clinical Nutrition

• Cat Food Carbohydrate & Dry Matter Basis (DMB) Calculator – Convert wet, canned, or dry cat food Guaranteed Analysis labels into true Dry Matter Basis (DMB) nutrient percentages and calculate Nitrogen-Free Extract (NFE) carbohydrate calories for diabetic felines.

Veterinary Palliative Care

• Pet Quality of Life Calculator (HHHHHMM Scale) – Assess your ailing or geriatric dog or cat's well-being using Dr. Alice Villalobos's validated veterinary HHHHHMM scale (Hurt, Hunger, Hydration, Hygiene, Happiness, Mobility, More Good Days Than Bad).

Canine Pharmacology

• Dog OTC Medication Dosage Calculator (Benadryl, Pepcid, Zyrtec) – Calculate safe canine weight-based dosages for Diphenhydramine (Benadryl), Famotidine (Pepcid AC), and Cetirizine (Zyrtec) with strict toxicity warnings against xylitol, pseudoephedrine, and acetaminophen.

Herpetoculture & Reptiles

• Snake Enclosure Size & Thermal Gradient Calculator – Calculate species-appropriate vivarium dimensions, 3-zone thermal gradient (basking, ambient warm, cool retreat), and Ferguson Zone UVB index across Ball Pythons, Corn Snakes, Boas, and Colubrids.

Workplace & Payroll

• Work Hours Calculator & Time Card Punch – Calculate total weekly hours worked, break time deductions, regular vs overtime hours (over 40 hrs/wk or 8 hrs/day), and gross paycheck earnings across a Monday-Sunday timesheet.

Finance & Compensation

• Paycheck Calculator & Hourly to Annual Salary Converter – Convert between hourly wage and annual salary, and calculate gross paycheck amounts across weekly, biweekly, semimonthly, and monthly pay frequencies.

Commerce & Business Math

• Margin and Markup Calculator – Calculate profit margin, markup percentage, cost of goods sold (COGS), and revenue selling price to protect profitability and avoid pricing confusion.

Metabolic & Nutritional Science

• TDEE Calculator & Calorie Deficit Macro Planner – Calculate your Total Daily Energy Expenditure (TDEE) and Basal Metabolic Rate (BMR) via Mifflin-St Jeor and Katch-McArdle equations, with custom caloric deficit targets and macronutrient distributions.

Financial Mathematics

• Compound Interest Calculator & Investment Growth – Calculate future investment value, compound interest earnings, and the growth of recurring monthly contributions over time across annual, quarterly, monthly, and daily compounding intervals.

Phylogenetics

• Phylogenetic Tree Maker – Free phylogenetic tree maker that runs in your browser. Paste aligned or unaligned DNA or protein sequences in FASTA format and get neighbor-joining and UPGMA trees side by side, bootstrap support values, a Fitch parsimony score, outgroup or midpoint rooting, a phylogram or cladogram, the distance matrix as CSV, and SVG and Newick downloads. Or paste a Newick tree from IQ-TREE, RAxML-NG, MEGA or MrBayes to draw and re-root it.

Genomics

• Sequencing Coverage Calculator – Calculate whole-genome or target-region sequencing coverage from read count, read length and paired-end setting, or the number of reads needed for a target depth such as 30×. Includes genome presets, a usable-read adjustment for duplicates and QC, and the expected fraction of the genome covered.

Physiology

• Q10 Temperature Coefficient Calculator – Calculate the Q10 temperature coefficient of a biological or chemical rate measured at two temperatures, or predict the rate at another temperature from a known Q10, with the working and a rate-versus-temperature curve.