Molecular Weight Calculator
Find the molecular weight of organic and inorganic compounds by formula.
How It Works
Type your compound formula using standard element symbols and numeric subscripts. The calculator sums atomic weights from IUPAC 2021 values. Parentheses are not supported; expand groups manually (e.g. Ca(OH)2 as CaO2H2).
Formula
MW = Σ (atomic weight × count) for all atoms
Examples
CO2 = 44.009 g/mol | NH3 = 17.030 g/mol | C2H5OH (ethanol) = 46.068 g/mol
Frequently Asked Questions
What unit is molecular weight in?
Molecular weight is expressed in daltons (Da) or g/mol. They are numerically equivalent: 1 Da = 1 g/mol.
How is molecular weight different from atomic mass?
Atomic mass is the mass of a single atom. Molecular weight is the sum of atomic masses of all atoms in a molecule.
Is CO2 molecular weight 44?
Yes. CO2 has 1 carbon (12.011) + 2 oxygen (2 × 15.999 = 31.998) = 44.009 g/mol.