Chemical Molar Mass Calculator
Calculate the molar mass of common chemical compounds.
Enter element symbols and counts to get the molecular weight in g/mol.
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is a fundamental quantity in chemistry, used for converting between mass and moles and for preparing solutions of precise concentration.
What is a Mole?
A mole is a specific number of particles: exactly 6.022 × 10²³ (Avogadro’s number). For any pure element, the molar mass in g/mol equals the atomic mass shown on the periodic table.
Calculating Compound Molar Mass
To find the molar mass of a compound, sum the atomic masses of all atoms in the formula:
M = Σ (atomic mass × number of atoms)
Example: Water (H₂O)
- 2 × H = 2 × 1.008 = 2.016 g/mol
- 1 × O = 1 × 15.999 = 15.999 g/mol
- Total: 18.015 g/mol
Example: Sodium Chloride (NaCl)
- 1 × Na = 22.990 g/mol
- 1 × Cl = 35.453 g/mol
- Total: 58.443 g/mol
Reference Atomic Masses (IUPAC 2021)
| Element | Symbol | Atomic Mass (g/mol) |
|---|---|---|
| Hydrogen | H | 1.008 |
| Carbon | C | 12.011 |
| Nitrogen | N | 14.007 |
| Oxygen | O | 15.999 |
| Sodium | Na | 22.990 |
| Magnesium | Mg | 24.305 |
| Sulfur | S | 32.06 |
| Chlorine | Cl | 35.45 |
| Potassium | K | 39.098 |
| Calcium | Ca | 40.078 |
| Iron | Fe | 55.845 |
| Copper | Cu | 63.546 |
Why Molar Mass Matters
Chemists use molar mass constantly for:
- Preparing solutions of known concentration (molarity = moles / volume)
- Stoichiometry — converting between masses in chemical reactions
- Calculating empirical and molecular formulas
- Understanding reaction yields