Compute the molar mass of any chemical formula with per-element breakdown.

Type a chemical formula — parentheses and hydrates are supported, e.g. Ca(OH)2 or CuSO4·5H2O.

Could not parse this formula — check element symbols and brackets.
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Element breakdown

Element Atoms Mass (g/mol) % of mass
Molar mass g/mol
Uses IUPAC 2021 standard atomic weights, rounded to 4 significant figures.

About Molar Mass Calculator

The molar mass calculator computes the molecular weight of any chemical formula in grams per mole. Type a formula such as H2O, C6H12O6, or Ca(OH)2 and the tool parses it, multiplies each element’s standard atomic weight by its atom count, and sums the result — with full support for parentheses and hydrates like CuSO4·5H2O.

Beyond the total, you get a per-element breakdown: how many atoms of each element the formula contains, the mass each element contributes, and its percentage of the total mass. That mass-percent column is exactly what you need for percent-composition problems in chemistry homework and stoichiometry calculations.

The calculator uses the IUPAC 2021 standard atomic weights rounded to four significant figures, and every parse happens instantly in your browser as you type — no lookup tables, no waiting, free for students, teachers, and lab work alike.

How to use Molar Mass Calculator

  1. Type the chemical formula into the input field — element symbols are case-sensitive, so write CO for carbon monoxide and Co for cobalt.
  2. Use parentheses for groups, e.g. Ca(OH)2, and a dot or middle dot for hydrates, e.g. CuSO4·5H2O.
  3. Read the molar mass in g/mol at the top of the results.
  4. Review the element breakdown table for atom counts, per-element mass, and percent of total mass.
  5. Try one of the example formulas if you want to see how a tricky structure is parsed.

Frequently asked questions

Each element’s standard atomic weight is multiplied by the number of atoms of that element in the formula, and the products are summed. For H2O: 2 × 1.008 + 1 × 16.00 ≈ 18.02 g/mol.

Yes. Nested groups like Al2(SO4)3 are expanded correctly, and hydrate notation such as CuSO4·5H2O adds the water molecules to the total. If a formula can’t be parsed, the tool tells you to check symbols and brackets.

The IUPAC 2021 standard atomic weights, rounded to four significant figures. That matches the values printed on most modern periodic tables and is accurate enough for coursework and routine lab calculations.

Numerically they are the same for a given formula. Molar mass is expressed in g/mol (mass of one mole of the substance), while molecular weight is the dimensionless relative mass. Chemists use the terms almost interchangeably.

It shows each element’s share of the compound’s total mass — the percent composition. In water, oxygen contributes about 88.8% of the mass and hydrogen about 11.2%.


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