Science & Engineering
Molar Mass Calculator - Molecular Weight from Formula
Enter a chemical formula (e.g. H₂O, NaCl, C₆H₁₂O₆) and instantly calculate molar mass with a per-element breakdown. Supports parentheses and nested groups.
How to calculate molar mass
Molar mass equals the sum of (atomic mass × atom count) for every element in the formula. For water (H₂O): (1.008 × 2) + (15.999 × 1) = 18.015 g/mol.
Formula syntax guide
- Use the capitalised element symbol from the periodic table: H, Na, Fe, Ca.
- Write the atom count immediately after the symbol: H2O, C6H12O6.
- Omit "1" - a bare symbol means one atom: NaCl = Na¹Cl¹.
- Use parentheses for repeating groups: Ca(OH)2 = CaO₂H₂.
Common molar masses
| Compound | Formula | Molar mass (g/mol) |
|---|---|---|
| Water | H₂O | 18.015 |
| Carbon dioxide | CO₂ | 44.010 |
| Sodium chloride (table salt) | NaCl | 58.44 |
| Glucose | C₆H₁₂O₆ | 180.156 |
| Sucrose (table sugar) | C₁₂H₂₂O₁₁ | 342.297 |
| Ethanol | C₂H₅OH | 46.069 |
| Sulfuric acid | H₂SO₄ | 98.079 |
| Sodium hydroxide (lye) | NaOH | 39.997 |
| Ammonia | NH₃ | 17.031 |
| Acetic acid (vinegar) | CH₃COOH | 60.052 |
| Baking soda | NaHCO₃ | 84.007 |
| Calcium carbonate (chalk) | CaCO₃ | 100.087 |
| Iron(III) oxide (rust) | Fe₂O₃ | 159.688 |
| Aspirin | C₉H₈O₄ | 180.159 |
| Caffeine | C₈H₁₀N₄O₂ | 194.194 |
The mole concept
A mole (symbol: mol) is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 10²³ entities (atoms, molecules, ions, or other particles) - Avogadro's number. This bridges atomic-scale mass to laboratory-scale mass:
- 1 mole of H₂O weighs 18.015 g (its molar mass in grams).
- 1 mole of NaCl weighs 58.44 g.
- 1 atom of carbon-12 weighs exactly 12 atomic mass units (u); 1 mole of C-12 weighs 12 g.
Hydrate syntax
For hydrated salts, use a dot to separate the anhydrous compound from the water molecules. For example, copper(II) sulfate pentahydrate is entered as:
CuSO4·5H2OMolar mass = 63.546 + 32.065 + 4×15.999 + 5×(2×1.008 + 15.999) = 249.685 g/mol.