Molar Mass Calculator

What is molar mass?

Molar mass is the mass of one mole, about 6.022 × 10²³ particles, of a substance, expressed in grams per mole. It links the microscopic world of atoms to the quantities you can weigh on a balance. Water, H2O, has a molar mass of about 18.015 g/mol: two hydrogen atoms at 1.008 each plus one oxygen atom at 15.999. This calculator parses any chemical formula, looks up each element in a built-in periodic table of all 118 elements, and adds up the contributions.

How the formula parser works

Type the formula the way you would write it in a textbook. Element symbols begin with a capital letter, optionally followed by a lowercase one, and a number after a symbol or a closing bracket multiplies it. Round, square and curly brackets can be nested, so Al2(SO4)3 and K4[Fe(CN)6] work. Hydrates and other adducts separated by a dot, like CuSO4·5H2O, are handled by multiplying the part after the dot by its leading coefficient. Unicode subscripts such as H₂O are accepted too. If a symbol is unknown or a bracket is unbalanced, you get a clear error message instead of a wrong number.

Mass percent and mole conversions

The breakdown table shows how many atoms of each element are present, their atomic mass, the combined mass and the mass percent composition, which is useful for empirical formula problems and purity checks. Enter a sample mass in grams to convert it to moles by dividing by the molar mass; multiply moles by the molar mass for the reverse. Atomic weights are standard values rounded to the precision most courses use, so results may differ slightly from tables that use other rounding. Everything is calculated locally in your browser and nothing is uploaded.