Molar Mass Calculator

Work out the molar mass of any formula with a per element breakdown and the percentage composition.

Molar mass and composition

Chemical formula

Molar mass: —

Elements: — · Total atoms: —

Note: —

—

Standard atomic weights are used, so the molar mass is reported in grams per mole for the formula you type.

Type the chemical formula, using brackets and subscripts as they are normally written.
Press Calculate to get the molar mass in grams per mole.
Read the per element table with atom counts and percentage composition.

Common questions about the free online molar mass calculator.

Type a formula such as Ca(OH)2, then read the molar mass in grams per mole together with the breakdown for every element.

Molar mass is the mass of one mole of a substance in grams, and it is numerically equal to the molecular weight in atomic mass units.

The tool uses a built in table of standard atomic weights, so the results match the values printed on most periodic tables.

Each element subtotal is its atom count times its atomic weight. Dividing that subtotal by the total molar mass gives the percentage.

Yes. Groups in brackets such as (OH)2 or (SO4)3 are multiplied out before the molar mass of the formula is added up.

Yes. Write the dot as a period, so CuSO4.5H2O adds five water units to the copper sulfate part of the formula.

Yes, a number such as 2 in 2H2O is accepted, but it only scales the whole formula and does not change the molar mass.

The molar mass is shown to three decimal places, which is enough for nearly all laboratory and homework calculations.

The tool tells you which symbol it could not find in the atomic weight table, so you can check the spelling of the formula.

No, the molar mass calculator runs locally in your browser and never uploads the formula you type.

Last updated: October 10, 2026