Molecular Weight Calculator
Enter a chemical formula and calculate molecular weight, molar mass, formula weight, elemental composition, and percent composition.
Quick answer: Type a formula such as H2O, NaCl, Ca(OH)2, or C6H12O6. The calculator sums standard atomic weights to return g/mol.
Presets
Enter a formula to calculate molecular weight.
How Molecular Weight Is Calculated
Molecular weight, also called molar mass or formula weight, is calculated by multiplying each element count by its atomic weight and summing the values. The result is reported in g/mol for one mole of formula units.
- H2O: 2 hydrogens plus 1 oxygen.
- Ca(OH)2: parentheses multiply oxygen and hydrogen by 2.
- Al2(SO4)3: nested-style formula groups are expanded before summing.