MasterTool

Molar Mass Calculator

Work out the molar mass of any compound from its formula — full element-by-element breakdown using IUPAC atomic weights.

IUPAC atomic weights last updated · reference source

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Dated static reference; no live data is fetched. Verify current source values and assumptions before relying on results.

What this tool does

Work out the molar mass of any compound from its formula — full element-by-element breakdown using IUPAC atomic weights. Uses IUPAC CIAAW conventional atomic weights (2021) — the standard values chemists use. Isotopes are averaged as they occur naturally, so a sample made of a single isotope would differ slightly.

How to use the Molar Mass Calculator

  1. Enter or select chemical formula.
  2. Read the calculated result; change any measurement to compare alternatives.

Formula

molar mass = Σ (atoms of each element × IUPAC atomic weight), parsed from the formula — parentheses multiply everything inside, and a '·' segment (hydrate water) is added with its coefficient.
formula
Chemical formula

Uses IUPAC CIAAW conventional atomic weights (2021) — the standard values chemists use. Isotopes are averaged as they occur naturally, so a sample made of a single isotope would differ slightly.

Worked example

For molar mass calculator, the following measurements illustrate the exact method: Chemical formula: H2O.

Inputs

  • Chemical formulaH2O

Result

  • Molar mass (g/mol)18.02
  • Total atoms per formula unit3
  • Elements present2

Results explained

Molar mass (g/mol)
Molar mass (g/mol) from the formula above. Uses IUPAC CIAAW conventional atomic weights (2021) — the standard values chemists use. Isotopes are averaged as they occur naturally, so a sample made of a single isotope would differ slightly.
Total atoms per formula unit
Total atoms per formula unit from the formula above. Uses IUPAC CIAAW conventional atomic weights (2021) — the standard values chemists use. Isotopes are averaged as they occur naturally, so a sample made of a single isotope would differ slightly.
Elements present
Elements present from the formula above. Uses IUPAC CIAAW conventional atomic weights (2021) — the standard values chemists use. Isotopes are averaged as they occur naturally, so a sample made of a single isotope would differ slightly.

Frequently asked questions

molar mass = Σ (atoms of each element × IUPAC atomic weight), parsed from the formula — parentheses multiply everything inside, and a '·' segment (hydrate water) is added with its coefficient.

Uses IUPAC CIAAW conventional atomic weights (2021) — the standard values chemists use. Isotopes are averaged as they occur naturally, so a sample made of a single isotope would differ slightly.

Type it as written: Ca(OH)2, Fe2(SO4)3, or CuSO4·5H2O (the middle dot can also be a full stop). Element symbols are case-sensitive — Co is cobalt while CO is carbon monoxide.

Numerically yes for most purposes: molecular weight is the (dimensionless) relative molecular mass, while molar mass is the same number expressed in g/mol — the mass of one mole of the substance.

Every field is labelled with its unit — enter values in exactly the labelled unit and read the result in the labelled output unit. Fields with a unit symbol also support the site-wide imperial/metric switch, which converts before the formula runs.

It uses double-precision arithmetic and the published constants and formulas named on this page. The last displayed digit may be rounded, and real conditions can differ from the idealized model described in the assumptions.

Yes. Every calculation runs entirely in your browser; nothing you enter is uploaded, stored or shared.