Molecular Weight Calculator
Calculate the molecular weight of any chemical compound from its formula. Shows each element's contribution.
Common formulas
Input format
Use capitals for elements (H, O, Na) followed by numbers for quantity
Molecular Weight
18.015 g/mol
Formula: H2O
Element breakdown
| Element | Symbol | Atomic mass | Count | Contribution |
|---|---|---|---|---|
| Hydrogen | H | 1.008 | 2 | 2.016 |
| Oxygen | O | 15.999 | 1 | 15.999 |
| Total | 18.015 | |||
Percentage composition
H(11.2%)
O(88.8%)
What is molecular weight?
Molecular weight (or molecular mass) is the sum of the atomic masses of all atoms in a molecule. It's expressed in atomic mass units (u) or g/mol.
How to calculate it
Multiply each element's atomic mass by the number of atoms of that element in the formula, then sum all results.
Applications
Molecular weight is essential for stoichiometric calculations, molar solution preparation, and converting between mass and moles.