Molecular Weight Calculator
Calculate the molecular mass (g/mol) and elemental percentage composition of chemical formulas using official IUPAC standard atomic weights.
How It's Calculated
Formula
M = \sum_{i} n_i \cdot A_{r,i}Molecular weight (or molar mass) is the sum of the atomic masses of all atoms present in a given chemical formula, measured in grams per mole (g/mol) or daltons (Da). Standard atomic weights are established by IUPAC and the Commission on Isotopic Abundances and Atomic Weights (CIAAW).
Worked Examples
Sulfuric Acid (H2SO4) Molar Mass
- Hydrogen (H): 2 atoms × 1.008 g/mol = 2.016 g/mol.
- Sulfur (S): 1 atom × 32.06 g/mol = 32.06 g/mol.
- Oxygen (O): 4 atoms × 15.999 g/mol = 63.996 g/mol.
- Total molecular weight = 2.016 + 32.06 + 63.996 = 98.072 g/mol.
Frequently Asked Questions
What units are used for molecular weight?
Molecular weight is typically expressed in grams per mole (g/mol), which is numerically identical to unified atomic mass units (u) or Daltons (Da).
Can I enter formulas with parentheses?
Yes. Formulas with parentheses and group multipliers like Ca(OH)2 or (NH4)2SO4 are fully supported.
Where do the atomic weight values come from?
All atomic weights are sourced from the Commission on Isotopic Abundances and Atomic Weights (CIAAW) under the International Union of Pure and Applied Chemistry (IUPAC).