Molar Mass Calculator

Type any chemical formula — including brackets and hydrates — to get its molar mass and the mass percentage of every element. Then convert between grams and moles.

StoichiometryCompositionMoles

Inputs

Input examples

Type _ for a subscript (H_2O gives H₂O); plain H2O works too. The keyboard button in the field has a chemistry tab with elements, subscripts and brackets. Type a formula such as Ca(OH)2 or CuSO4·5H2O (use ·, * or . for hydrates). Element symbols are case-sensitive: Co is cobalt, CO is carbon monoxide.

Chemical formula

H_{2}SO_{4}

Mass ↔ moles — optional

Mass m

Amount n

What is Molar Mass?

The molar mass M is the mass of one mole of a substance — 6.022×10²³ particles. Numerically it equals the sum of the atomic masses in the formula, expressed in grams per mole.

Molar mass is the bridge between what you can weigh (grams) and what reacts (numbers of particles). Every stoichiometry calculation starts by turning grams into moles with n = m / M.

H₂O18.015 g/mol

1 mol6.022×10²³ particles

( )₂brackets multiply

·5H₂Owater of crystallisation

Mass Composition

H₂SO₄

Result

Enter a formula above

Common Compounds

Compound	Formula	M (g/mol)
Water	H₂O	18.015
Carbon dioxide	CO₂	44.009
Table salt	NaCl	58.44
Ethanol	C₂H₅OH	46.07
Glucose	C₆H₁₂O₆	180.16
Sulfuric acid	H₂SO₄	98.07
Calcium carbonate	CaCO₃	100.09

Working with Formulas

Summing Atomic Masses

Multiply each element’s atomic mass by how often it appears, then add everything up. Atomic masses come from the periodic table.

Example:

Mass Percentage

The share of the total mass that comes from one element — useful for analysing ores, fertilisers and empirical formulas.

Example:

Grams to Moles

Divide a mass by the molar mass to count moles — the first step of every reaction calculation.

Example:

Sources & Verification

References

S. S. Zumdahl & S. A. Zumdahl, Chemistry, 10th ed., Cengage, 2018 — Ch. 3 (Stoichiometry).
T. Prohaska et al., “Standard atomic weights of the elements 2021 (IUPAC Technical Report)”, Pure and Applied Chemistry 94(5), 573–600 (2022) — atomic weights.