Molar mass calculator
Type a chemical formula to get its molar mass, the element breakdown, and percent composition.
Formulas are case-sensitive: Co is cobalt, CO is carbon monoxide. Use parentheses for groups and a dot or * for hydrates.
g/mol
Grams and moles
How the calculation works
Molar mass is the mass of one mole of a substance. The calculator counts each element in your formula, multiplies by its standard atomic weight, and adds the results. Percent composition is each element’s share of that total.
Example: water, H2O, has two hydrogens (2 × 1.008) and one oxygen (15.999), so its molar mass is 18.015 g/mol. Atomic weights are rounded standard values, which is what most textbooks and lab courses use.