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
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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