Molecular Weight Calculator
Enter a chemical formula to find its molar mass (g/mol), with a breakdown by element.
– g/mol
| Element | Atoms | Atomic mass | Subtotal |
|---|
Try: H2O NaCl C6H12O6 Ca(OH)2 CuSO4·5H2O
Molecular weight (molar mass) calculator
This calculator works out the molecular weight, or molar mass, of any compound from its chemical formula. Type a formula such as H2O, NaCl, or C6H12O6 — including brackets like Ca(OH)2 — and it returns the molar mass in grams per mole (g/mol), with a breakdown showing how each element contributes.
How molar mass is calculated
The molar mass of a compound is the sum of the atomic masses of all the atoms in its formula. For water (H₂O), that is two hydrogen atoms (2 × 1.008) plus one oxygen atom (1 × 15.999), giving 18.015 g/mol. The calculator parses your formula, multiplies each element’s atomic mass by how many atoms appear, and adds the results together.
Why molar mass matters
Molar mass is the bridge between the mass of a substance and the number of moles it contains (moles = mass ÷ molar mass). It is essential for preparing solutions, balancing reactions, and stoichiometry. Pair this with our chemistry calculator for moles and molarity, and the dilution calculator for solution prep.
Frequently asked questions
How do I enter brackets and hydrates?
Brackets work as written, e.g. Ca(OH)2. For hydrates you can write the water of crystallisation directly, e.g. CuSO4·5H2O or CuSO45H2O.