Molar Mass Calculator
Enter any chemical formula to instantly get its molar mass, element by element, from IUPAC atomic weights.
e.g. "H2O", "C6H12O6", "Ca(OH)2", "Al2(SO4)3". Case matters: Co is cobalt, CO is carbon+oxygen.
| Element | Count | Atomic weight (g/mol) | Subtotal |
|---|---|---|---|
| Ca | 1 | 40.078 | 40.078 |
| H | 2 | 1.008 | 2.016 |
| O | 2 | 15.999 | 31.998 |
| Total | 74.092 | ||
Atomic weights: IUPAC Standard Atomic Weights, iupac.qmul.ac.uk/AtWt (fetched 2026-09-19).
What Is Molar Mass?
Molar mass is the total mass of one mole of a substance, found by summing each element's atomic weight, multiplied by how many atoms of that element appear in the formula. It's the conversion factor between a mass you can weigh on a scale and a mole count you can use in a chemical equation.
This calculator parses the formula string directly, including parenthesized groups like Ca(OH)2 or Al2(SO4)3, and pulls every atomic weight from IUPAC's official Standard Atomic Weights table rather than a hardcoded guess.
Worked example
Find the molar mass of glucose, C6H12O6.
6 × 12.011 (C) + 12 × 1.008 (H) + 6 × 15.999 (O) = 72.066 + 12.096 + 95.994
= 180.156 g/mol.
Common mistake
Forgetting that a subscript after a closing parenthesis multiplies everything inside it. Al2(SO4)3 has 3 sulfur atoms and 12 oxygen atoms (4 x 3), not 1 sulfur and 4 oxygen.
Keep going
- Molar mass is the conversion factor between mass and moles; the mole calculator applies it directly to turn a mass into a mole count. Moles Calculator
- Molar mass sums a known formula's atomic weights; empirical formula works the other direction, deriving a formula from measured element masses. Empirical Formula Calculator
Frequently Asked Questions
What is molar mass?
Molar mass is the mass of one mole (6.022 x 10^23 particles) of a substance, in grams per mole (g/mol). It's found by adding up the atomic weights of every atom in the formula, each multiplied by how many times it appears.
Is molar mass the same as molecular weight?
For practical purposes, yes -- molecular weight is technically a dimensionless ratio and molar mass carries units of g/mol, but they're numerically identical for a given compound and the terms are used interchangeably in chemistry.
How does the formula parser handle parentheses?
A group in parentheses, like the (OH) in Ca(OH)2, is multiplied entirely by the number after the closing parenthesis -- so Ca(OH)2 means 1 Ca, 2 O, and 2 H, not 1 O and 1 H.
Does capitalization matter in a formula?
Yes, and it matters a lot: Co is the element cobalt, but CO is one carbon atom and one oxygen atom (carbon monoxide). Always capitalize only the first letter of a two-letter element symbol.
Where do the atomic weights come from?
IUPAC's official Standard Atomic Weights table (iupac.qmul.ac.uk/AtWt), the internationally recognized reference every periodic table is built from. This calculator cites the exact conventional value used for each element.
Related Calculators
- Moles Calculator — Atomic & Molecular
- Empirical Formula Calculator — Atomic & Molecular
- Atomic Mass Calculator — Atomic & Molecular
- Half-Life Calculator — Atomic & Molecular