Lightweight formula parser
This calculator covers common formula notation and a practical element table for everyday chemistry examples. For advanced isotopic composition, use a chemistry reference database.
Example
For water, H2O, the molar mass is based on two hydrogen atoms and one oxygen atom. Using common rounded atomic weights, that is about 2 x 1.008 + 15.999 = 18.015 g/mol.
Common mistakes
Use proper capitalization for element symbols. CO means carbon monoxide, while Co is cobalt. Parentheses also matter: Ca(OH)2 has two oxygen atoms and two hydrogen atoms from the repeated OH group.
Limitations
Atomic weights are averages, so exact mass can differ for a specific isotope or isotope-enriched sample. This calculator is intended for ordinary molar-mass work, not high-precision analytical chemistry.
Last reviewed: 2026-05-17