Molar mass is the mass of one mole (6.022 × 10²³ molecules) of a substance, expressed in grams per mole (g/mol). It equals the sum of the atomic masses of all atoms in the molecular formula.

How do I write a molecular formula?

Use the element symbol followed by the atom count as a plain number: H2O, C6H12O6, NaCl. For groups, use parentheses followed by the multiplier: Ca(OH)2, Al2(SO4)3.

Are the atomic masses exact?

The tool uses standard atomic weights from IUPAC (2021), which are weighted averages over natural isotope abundances. They match values found in textbooks and are accurate to 4–5 significant figures.

What is the difference between molar mass and molecular weight?

Molar mass (g/mol) and molecular weight (unified atomic mass units, u) are numerically identical for a given formula — only the units differ. Both are commonly called "molecular weight" in practice.

Does this support hydrates like CuSO4·5H2O?

Yes — use the middle dot as a separator: CuSO4·5H2O or type the dot as a period CuSO4.5H2O. The tool treats it the same as multiplying the trailing formula by its coefficient.

Molar Mass Calculator

Enter a molecular formula like H2O or C6H12O6 and get the molar mass in g/mol with a full element breakdown.

Molecular Formula

Chemical Formula

Use element symbols with numeric subscripts. Parentheses supported: Ca(OH)2.

Quick examples:

Enter a molecular formula and click Calculate

Molar Mass

— g/mol

Formula (parsed)

—

Element Breakdown

Element	Count	Atomic Mass	Contribution

Mass Percent Composition

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Summary

The Molar Mass Calculator computes the molecular weight of any chemical compound from its formula. Type a formula such as H2O, NaCl, or C6H12O6 and the tool parses each element and subscript, looks up atomic masses from the periodic table, and returns the total molar mass in g/mol along with a breakdown by element. Parentheses and nested groups like Ca(OH)2 or Al2(SO4)3 are fully supported.

How it works

Type a molecular formula into the input field (e.g., H2O, NaCl, Fe2O3).
The tool parses every element symbol and its subscript count.
Parenthesized groups like Ca(OH)2 are expanded before parsing.
Atomic masses from the standard periodic table are multiplied by each element count.
The individual contributions are summed to give the total molar mass in g/mol.
An element breakdown table shows each atom's contribution to the total mass.

Use cases

Stoichiometry calculations in chemistry homework and lab work.
Converting between grams and moles for a reagent.
Verifying the molecular weight of a synthesized compound.
Preparing solutions of a known molarity.
Quick periodic-table lookups for atomic masses during an exam.
Teaching balancing chemical equations and mole concepts.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu