PPM Calculator

Convert ppm, ppb, mg/L, percent and molarity, or work out how much to weigh.

In a dilute water solution 1 ppm equals 1 mg/L, 1 µg/mL and 1000 ppb. 1 % w/v is 10,000 ppm. To convert ppm to molarity divide mg/L by 1000 and then by the molar mass: 250 ppm NaCl is 0.25 g/L ÷ 58.44 g/mol = 4.28 mM. To make a solution, mass (mg) = ppm × volume (L).

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Formula

1 ppm = 1 mg/L = 1 µg/mL = 1000 ppb   |   % w/v = ppm / 10,000   |   M = (mg/L) / (1000 × MW)   |   mass (mg) = ppm × V (L)

ppm is a mass ratio, mg of solute per kg of solution. For dilute aqueous solutions the density is taken as 1.000 kg/L, so a kilogram of solution is one litre and mg/kg equals mg/L. This breaks down for concentrated solutions, organic solvents and seawater, where the real density must be used.

Questions

Is 1 ppm equal to 1 mg/L?

Yes for dilute solutions in water, because a litre of such a solution weighs very close to 1 kg. For dense solutions or other solvents, mg/L = ppm × density in kg/L.

How do you convert ppm to molarity?

Divide ppm (mg/L) by 1000 to get g/L, then divide by the molar mass in g/mol. For 100 ppm glucose (180.16 g/mol), 0.1 ÷ 180.16 = 0.555 mM.

How much solute do I need to make a ppm solution?

Multiply the target ppm by the final volume in litres to get milligrams. For 50 ppm in 500 mL you need 50 × 0.5 = 25 mg, dissolved and made up to 500 mL.

How do I convert ppm to percent?

Divide by 10,000. So 2500 ppm is 0.25 %, and 1 % is 10,000 ppm.

What is the difference between ppm and ppb?

1 ppm is 1000 ppb. In water, ppm is mg/L and ppb is µg/L.

How do I make a ppm solution from a stock?

Use C1V1 = C2V2. To make 500 mL of 50 ppm from a 1000 ppm stock, take 50 × 500 ÷ 1000 = 25 mL of stock and make it up to 500 mL.

References

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All free tools · By Dr. Zubair Khalid, DVM, MS, PhD.