Math
Molar Mass Calculator
Compute molar mass from any chemical formula. Parses H2O, NaCl, C6H12O6, Ca(OH)2, Fe2(SO4)3, and hydrates like CuSO4.5H2O. Shows per-element mass percents.
Molar Mass Calculator
Use standard element symbols. Capital first letter, optional lowercase second letter. Group with parentheses; mark hydrates with a dot (.) or asterisk (*).
Molar mass
18.015 g/mol
3 atoms across 2 elements. Empirical formula: H2O.
| Element | Count | Atomic mass | Contribution | Mass % |
|---|---|---|---|---|
| H | 2 | 1.008 | 2.016 | 11.1907% |
| O | 1 | 15.999 | 15.999 | 88.8093% |
Frequently Asked Questions about the Molar Mass Calculator
What is molar mass?
Molar mass is the mass in grams of one mole (6.022 x 10^23 entities) of a substance. For water (H2O), the molar mass is about 18.015 g/mol because two hydrogen atoms (2 x 1.008) plus one oxygen (15.999) sum to 18.015.
How do I write a chemical formula the calculator understands?
Use standard chemistry notation: element symbols with proper capitalization, numbers as subscripts written inline. H2O, NaCl, C6H12O6, Ca(OH)2, Fe2(SO4)3, and hydrates like CuSO4.5H2O all work. The dot for hydrates can be "." or "*".
Where do the atomic weights come from?
From the IUPAC standard atomic weights, the values printed on every modern periodic table. The calculator covers elements 1 through 80 (hydrogen through mercury), which spans every commonly encountered formula in chemistry, biology, and engineering.
How do I convert mass to moles?
Divide grams by molar mass. For 9 g of water: 9 / 18.015 = 0.4996 mol. To go the other way, multiply moles by molar mass. The calculator displays the molar mass so you can do that conversion yourself, or input a sample mass for quick conversion.
Why are the percent masses useful?
Percent composition tells you what fraction of a compound's mass comes from each element. For glucose (C6H12O6), carbon contributes about 40%, hydrogen 6.7%, and oxygen 53.3%. That helps you reason about empirical formulas, fertilizer N-P-K labels, and combustion stoichiometry.