Molar Mass Calculator

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.

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 "*".

The values are based on standard atomic weights. This calculator includes elements 1 through 80, hydrogen through mercury. Formulas containing later elements, including lead, bismuth, uranium, or synthetic elements, are outside its current element table and will not parse.

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.

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.