Molar Mass Calculator
Type any chemical formula — H₂O, Fe₂(SO₄)₃, CuSO₄·5H₂O — and get its molar mass in g/mol with a full breakdown per element. Free, instant and private.
What is molar mass?
Molar mass is the mass of one mole of a substance, in grams per mole (g/mol). For a molecule, add the relative atomic masses of every atom in the formula — the molar mass of H₂O, for example, is 2 × 1.008 (hydrogen) + 15.999 (oxygen) ≈ 18.02 g/mol.
You can use brackets — Fe₂(SO₄)₃ — and hydrated compounds such as CuSO₄·5H₂O (copper(II) sulfate pentahydrate): type the water of crystallization with a dot (·), a period (.) or an asterisk (*). Molar mass is what connects grams to moles in every lab calculation: n = m / M.
Atomic masses are mean relative atomic masses in g/mol. For elements without a stable isotope, the mass of the longest-lived isotope is used. Values follow the Periodic-Table-JSON dataset.