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chemistryClassic tool

Molecular Weight Calculator

Calculate molecular weight and molar mass from a chemical formula, including parentheses, hydrates and repeated groups.

Use this molecular weight calculator to find the molar mass of compounds, salts, oxides, acids and hydrates without adding every atomic mass by hand. It reads the chemical formula and returns the total in g/mol.

Enter formulas such as H2O, NaCl, Ca(OH)2, Fe2(SO4)3 or CuSO4·5H2O. The tool handles multipliers, repeated groups and common hydrate notation, then shows a clear element-by-element breakdown.

It is useful for homework, lab prep, solution planning, stoichiometry checks and quick comparisons before converting grams to moles or reviewing reaction inputs.

Supports formulas like H2O, NaCl, Ca(OH)2, K4[Fe(CN)6] and hydrate dot notation.

SummaryEnter a chemical formula to calculate molecular weight.
Molar mass—
Elements found—
Total atoms—
Normalized formula—
Element breakdown
The element breakdown will appear here.

Use clear inputs to get a more useful result.

How the calculation works

The calculator parses each element symbol, applies the multipliers for groups inside parentheses, brackets or braces, and adds the mass contribution of every atom. The final result is shown as an estimated molar mass in grams per mole.

Formula tips

  • Keep element symbols case-sensitive, such as NaCl, Fe2O3 and Mg(OH)2.
  • Hydrates can be written with a dot, such as CuSO4·5H2O.
  • Use the breakdown panel to verify where most of the mass comes from before moving on to stoichiometry or solution calculations.