Molecular Weight Calculator
Calculate the molecular weight of a chemical compound from its formula, including nested parentheses like Ca(OH)2.
- Free to use
- Accurate results
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- Works on all devices
Enter a chemical formula like H2O or Ca(OH)2 to find its molecular weight in g/mol.
Use standard notation, e.g. H2O, NaCl, Ca(OH)2, or Al2(SO4)3.
Your result
18.015
Molecular weight (g/mol)
Total atoms3
Distinct elements2
AI explanation
Formula
Molecular weight = sum of (atomic weight × atom count) for every element in the formulaWorked example
Water (H2O)
| Field | Value |
|---|---|
| Chemical formula | H2O |
| Molecular weight (g/mol) | 18.015 |
| Total atoms | 3 |
| Distinct elements | 2 |
Assumptions
- Uses standard IUPAC conventional atomic weights.
- Supports nested parentheses with a trailing multiplier (e.g. Ca(OH)2, Al2(SO4)3) but not other notations like hydrates (e.g. "CuSO4·5H2O") — enter each part's formula separately if needed.
Frequently asked questions
What formulas does this support?
Standard chemical notation with element symbols, numeric subscripts, and nested parentheses with a multiplier — e.g. H2O, NaCl, Ca(OH)2, Al2(SO4)3, or C6H12O6.
Does this support hydrate notation, like "CuSO4·5H2O"?
Not directly — calculate the anhydrous compound (CuSO4) and the water portion (H2O × 5) separately, then add the two molecular weights together.
How accurate are the atomic weights used?
Standard IUPAC conventional atomic weights are used, which are accurate to the precision typically needed for stoichiometry and lab calculations.