How to Calculate Molecular Weight
What is Molecular Weight?
Molar mass (molecular weight) is the mass of one mole (6.022 × 10²³ molecules) of a substance. It is calculated by summing the atomic masses of all atoms in the chemical formula.
Step-by-Step Guide
- 1Identify each element and its count in the formula
- 2Look up each element's atomic mass (from the periodic table)
- 3Multiply each atomic mass by its count
- 4Sum all values — the result is in g/mol
Worked Examples
Input
H₂O
Result
18.015 g/mol
2×1.008 + 15.999
Input
NaCl
Result
58.44 g/mol
22.99 + 35.45
Input
C₆H₁₂O₆ (glucose)
Result
180.16 g/mol
6×12 + 12×1.008 + 6×16
Ready to calculate? Try the free Molecular Weight Calculator
Try it yourself →