How to Calculate Molar Mass
What is Molar Mass?
A molar mass (molecular weight) calculator sums the atomic masses of all atoms in a chemical formula. Molar mass in g/mol numerically equals molecular weight in daltons (Da).
Formula
Molar mass (g/mol) = Σ (atomic masses of all atoms in molecule); Moles = mass (g) / molar mass (g/mol)
- M
- Molar mass (g/mol)
- A
- Atomic mass (u (atomic mass units))
- n
- Number of moles (mol)
Step-by-Step Guide
- 1Molar mass = Σ (atomic mass × number of each atom)
- 2Atomic masses from periodic table (in g/mol)
- 3H=1.008, C=12.011, N=14.007, O=15.999, Na=22.990, Cl=35.453
- 4Used to convert between grams and moles: n = m/M
Worked Examples
Input
Water (H₂O)
Result
2×1.008 + 15.999 = 18.015 g/mol
Input
Glucose (C₆H₁₂O₆)
Result
6×12.011 + 12×1.008 + 6×15.999 = 180.156 g/mol
Frequently Asked Questions
How do I calculate molar mass of H₂O?
(2 × 1.008) + 16.00 = 18.016 g/mol.
Why do I need molar mass?
Converts between grams (lab measurement) and moles (chemistry calculations). Essential for stoichiometry.
What's a mole?
6.022 × 10²³ particles (Avogadro's number). Standard unit for counting atoms/molecules in chemistry.
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