Free · No signup

Molecular Weight Calculator

Calculate the molecular weight of a chemical formula instantly.

Result expressed in g/mol (molar mass). What's the difference?

Examples:

Need to calculate solution concentration? Molarity Calculator →

Working with experimental data?

Create publication-ready scientific figures from Excel or CSV with FigureReady.

Create a scientific figure

Supported formula syntax

  • H2O, NaCl, C6H12O6 — standard element symbols with integer counts
  • Ca(OH)2, Fe2(SO4)3 — parentheses at any nesting depth
  • CuSO4·5H2O, CuSO4.5H2O — hydrates (middle dot or period)

Not supported in V1: ionic charges (Ca²⁺), isotopic notation (¹⁴C), fractional counts. Invalid syntax returns an explicit error — no silent partial calculation.

What is molecular weight?
Sum of the atomic masses of all atoms in a molecule, expressed in g/mol. Atomic masses from IUPAC 2021 (CIAAW).
Molecular weight vs molar mass
Numerically identical. Molecular weight is dimensionless; molar mass is in g/mol. Used interchangeably in practice. This calculator reports g/mol.
Ionic charges, isotopes, fractions
Not supported in V1. Ca²⁺, ¹⁴C, C3.5H5 will return an explicit error.
Next step: calculate molarity
Once you have the molar mass, use the Molarity Calculator to compute the concentration of your solution.