Molar Mass Calculator

Calculate the molar mass of a chemical formula — H2O, Ca(OH)2, C6H12O6, CuSO4·5H2O — with a breakdown of each element’s count, mass contribution and percentage by mass. Brackets, hydrates and charges are understood, and grams convert to moles.

This tool runs entirely in your browser.

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How to use the Molar Mass Calculator

1Type a formula with correct capitals: Co is cobalt, CO is carbon monoxide.
2Use brackets for groups, Ca(OH)2, and · or * for hydrates, CuSO4·5H2O.
3Read the molar mass and each element’s share by mass.
4Optionally enter a mass in grams to convert it to moles.

What is the Molar Mass Calculator?

Molar mass is the mass of one mole (6.022 × 10²³ formula units) of a substance in grams per mole. It is the sum of the atomic weights of every atom in the formula: water, H₂O, is 2 × 1.008 + 15.999 = 18.015 g/mol. The calculator uses IUPAC standard atomic weights and shows each element’s contribution and percentage by mass.

The parser handles nested brackets like K4[Fe(CN)6], Unicode subscripts, hydrate dots and a trailing ionic charge (SO4^2-, which is ignored because electrons weigh almost nothing). It also checks whether the formula can balance with the elements’ common oxidation states, and warns when something looks incomplete — such as H2SO instead of H2SO4.

Frequently asked questions

What is the molar mass of water?

18.015 g/mol: two hydrogens (2 × 1.008) plus one oxygen (15.999).

Is molar mass the same as molecular weight?

Numerically yes — molecular weight (in daltons, u) and molar mass (in g/mol) have the same number. Molar mass is the term for a mole of the substance.

How do I convert grams to moles?

Divide the mass by the molar mass: 36 g of water ÷ 18.015 g/mol ≈ 2.0 mol. Enter the grams below the result to do it automatically.

Is the Molar Mass Calculator free and private?

Yes. The Molar Mass Calculator is free, needs no account, and runs entirely in your browser. What you type is never sent to a server or stored.

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