Molecular Weight Calculator
Uses IUPAC standard atomic weights. Type formulas with capital-letter element symbols and no spaces — parentheses for grouped subscripts are supported (e.g. Al2(SO4)3).
Free molecular weight calculator — type any chemical formula (with parentheses for grouped subscripts) and get the exact molar mass using IUPAC standard atomic weights, plus the element breakdown.
How it works
- Type a chemical formula, like H2O, C6H12O6, or Al2(SO4)3
- Capital-letter element symbols, no spaces — parentheses for grouped subscripts are supported
- See the molecular weight in g/mol and the element-by-element breakdown
Frequently asked questions
Does it support parentheses?
Yes — including nested ones, like Al2(SO4)3 or Ca3(PO4)2. Each group's subscript multiplies everything inside the parentheses.
Where do the atomic weights come from?
IUPAC's standard atomic weights, the same reference values used in chemistry textbooks and periodic tables.
What if I mistype a formula?
It tells you exactly what went wrong — an unrecognized element symbol, mismatched parentheses, or an unexpected character — instead of silently giving a wrong number.
Related tools
From the blog
Update history
- 2026-09-02 Launched: molecular weight calculator with a full chemical formula parser (parentheses, nested groups) and IUPAC standard atomic weights for all 118 elements. Entirely client-side.