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.

The Molecular Weight Calculator parses a chemical formula such as C6H12O6, Ca(OH)2 or CuSO4·5H2O, multiplies each element's count by its IUPAC standard atomic weight and sums them to give the molar mass in g/mol, with the mass fraction of each element and the moles and molarity of a given mass in a given volume.

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How to use it

  1. Type the formula (or pick a preset).
  2. Read the molar mass and composition.
  3. Enter a mass and volume for molarity.

What you enter

What you get

Formula

M = Σ nᵢ · Aᵣ(elementᵢ)   |   moles = mass / M   |   molarity = moles / volume (L)

Atomic weights are the IUPAC 2021 standard values (conventional values where an interval is defined). Hydrate water and bracketed groups are expanded before summing.

Worked example

Input: CuSO4·5H2O

Result: 249.68 g/mol · Cu 25.45 %, S 12.84 %, O 57.66 %, H 4.04 %

Copper sulfate pentahydrate: 63.546 + 32.06 + 4(15.999) + 5(18.015).

Questions

What is the difference between molecular weight and molar mass?

Numerically the same for a compound; molecular weight is a dimensionless relative mass, molar mass is expressed in g/mol.

How do I enter a hydrate?

Use a dot or asterisk: CuSO4·5H2O or CuSO4*5H2O.

How do I convert grams to moles?

Divide the mass by the molar mass. The converter at the bottom does this and gives molarity for a chosen volume.

Limitations

References

Related reading

More Chemistry

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