Chemical Name Calculator

Chemistry

Look up the molecular weight of a simple compound by entering the number of atoms of each element.

Formula

MW = Σ (number of atoms × atomic mass)
  • Atomic masses (g/mol): C=12.011, H=1.008, O=15.999, N=14.007, S=32.06, Cl=35.45.
  • Only the most common elements are included. For other elements, add their masses manually.
  • Molecular weight equals molar mass in g/mol.

Methane (CH₄)

Inputs
  • Carbon (C) atoms: 1
  • Hydrogen (H) atoms: 4
  • Oxygen (O) atoms: 0
  • Nitrogen (N) atoms: 0
  • Sulfur (S) atoms: 0
  • Chlorine (Cl) atoms: 0

MW = 1×12.011 + 4×1.008 = 16.043 g/mol.

Frequently asked questions

What is molecular weight?
The sum of atomic masses of all atoms in a molecule, expressed in g/mol.
What is the difference between molecular weight and molar mass?
They are numerically equal — molar mass is in g/mol, molecular weight is dimensionless (in Da or u).