Molar Mass Calculator
Convert between grams and moles for any chemical formula, plus number of molecules and percent composition.
Formula
n = m / M ; m = n × M ; N = n × Nₐ
How to use
- 1Enter a chemical formula (e.g. NaCl, H2O, Ca(OH)2).
- 2Choose whether you are giving mass or moles.
- 3Enter the known value.
- 4Read molar mass, the converted amount, molecules, atoms and percent composition.
About this calculator
The mole is how chemists count enormous numbers of tiny particles, and molar mass is the bridge between the grams you weigh and the moles a reaction cares about. Type any chemical formula and this tool works out the molar mass, converts grams and moles either way, and reports molecules, total atoms and percent composition.
Formula explained
Three linked relationships: n = m ÷ M (moles from mass), m = n × M (mass from moles), and N = n × Nₐ (particles from moles), where Nₐ ≈ 6.022 × 10²³. Molar mass M is the sum of the atomic masses of every atom in the formula, so the tool parses the formula and adds up its elements.
Worked example
Na ≈ 22.99 + Cl ≈ 35.45 gives M ≈ 58.44 g/mol. n = 5.85 ÷ 58.44 ≈ 0.100 mol, which is N ≈ 0.100 × 6.022 × 10²³ ≈ 6.02 × 10²² formula units.
Tips & notes
- Watch capitalisation: Co is cobalt, CO is carbon monoxide.
- Carry a few significant figures and round only at the end.
- Values use standard atomic masses; very high-precision work may need isotope-specific figures.