Molar Mass Calculator
Enter any chemical formula to get its molar mass, with a per-element breakdown.
| Element | Count | Mass (u) | Subtotal |
|---|---|---|---|
| C | 6 | 12.011 | 72.066 |
| H | 12 | 1.008 | 12.096 |
| O | 6 | 15.999 | 95.994 |
To find molar mass, sum the standard atomic mass of every atom in the formula, in g/mol: molar mass = Σ (atomic mass × count). For water, H₂O, that is 2 × 1.008 + 15.999 = 18.015 g/mol — two hydrogens plus one oxygen.
How molar mass is calculated
The molar mass of a compound is the sum of the standard atomic masses of every atom in its formula, in grams per mole. The calculator parses your formula — including nested parentheses like Ca(OH)₂ — and multiplies each element’s atomic weight by how many times it appears, then adds the contributions together.
sum every element’s atomic weight times how many atoms appear
Worked example
Find the molar mass of water, H₂O — two hydrogen atoms and one oxygen.
- 1 Look up each atomic mass. Hydrogen is 1.008 g/mol and oxygen is 15.999 g/mol on the standard scale.
- 2 Multiply by the atom counts. Hydrogen: 2 × 1.008 = 2.016. Oxygen: 1 × 15.999 = 15.999.
- 3 Add the contributions. 2.016 + 15.999 = 18.015 g/mol for one mole of H₂O.
Molar masses of common compounds
Computed from standard atomic weights; values rounded to three decimals.
| Compound | Formula | Molar mass (g/mol) |
|---|---|---|
| Water | H₂O | 18.015 |
| Carbon dioxide | CO₂ | 44.009 |
| Table salt | NaCl | 58.440 |
| Glucose | C₆H₁₂O₆ | 180.156 |
| Calcium hydroxide | Ca(OH)₂ | 74.092 |
| Sulfuric acid | H₂SO₄ | 98.072 |
Reading a formula correctly
Subscripts apply to the atom before them. In CO₂ the 2 multiplies only the oxygen, giving one carbon and two oxygens. Each atomic weight is pulled from the same data behind the periodic table.
Parentheses distribute. In Ca(OH)₂ the 2 multiplies everything inside, so there are two oxygens and two hydrogens, not one of each.
Common mistakes. Forgetting to multiply a polyatomic group by its subscript, mixing up the atomic masses of similar symbols (for example Co cobalt vs CO carbon-and-oxygen), and rounding atomic masses too early. Keep full precision until the final sum.