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Molar Mass Calculator

Calculate the molar mass (molecular weight) of any compound from its chemical formula. The calculator parses the formula — including parentheses and hydrates — looks up each element's standard atomic weight, and adds them up to give the molar mass in grams per mole.

Compound
Element
Chemical formula

What Is Molar Mass?

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is numerically equal to the substance's atomic or molecular weight in atomic mass units (u).

To find it, add together the standard atomic weight of every atom in the chemical formula. For water (H₂O) that is two hydrogen atoms plus one oxygen atom.

Formula

Molar mass = Σ (atomic weight × number of atoms)

Example: Molar mass of water, H₂O:

2 × 1.008 (H) + 1 × 15.999 (O) = 18.015 g/mol


See also