Molar mass calculator
Type a chemical formula and get its molar mass in g/mol, with the share of each element. Parentheses, hydrates and ions included. Free in Periodic Table and Chemistry for iPhone, iPad and Mac.
How to calculate molar mass
- Count the atoms of each element in the formula. A subscript after parentheses multiplies everything inside: Ca(OH)₂ has 2 O and 2 H.
- Multiply each count by the element’s standard atomic weight (in g/mol).
- Add the products. The sum is the molar mass: the mass in grams of one mole of the substance.
Worked example: sulfuric acid, H₂SO₄
| Element | Atoms × atomic weight | g/mol | Mass % |
|---|---|---|---|
| H | 2 × 1.008 | 2.016 | 2.06 % |
| S | 1 × 32.06 | 32.06 | 32.69 % |
| O | 4 × 15.999 | 63.996 | 65.25 % |
| Molar mass of H₂SO₄ | 98.072 g/mol | ||
The mass percent of each element is its contribution divided by the molar mass: 63.996 / 98.072 = 65.25 % oxygen.
What the app does for you
- A chemistry keyboard with element symbols and subscripts, so H2SO4 becomes H₂SO₄ as you type.
- Parentheses and brackets, like Ca(OH)₂ or K₄[Fe(CN)₆], hydrates like CuSO₄·5H₂O and ions like SO₄²⁻.
- It tells Co (cobalt) from CO (carbon monoxide), and offers the other reading when a formula is ambiguous.
- The composition by element, with each atom’s contribution and mass percent, and a history of your calculations.
- Atomic weights checked against IUPAC and PubChem. Ask Siri: “Molar mass in Periodic Table”.
Questions.
- What is molar mass?
- The mass of one mole of a substance, in grams per mole (g/mol). It has the same number as the relative formula mass: water, H₂O, is 18.015 g/mol.
- Is the molar mass calculator free?
- Yes. The molar mass and the composition by element are free in the app, with no ads and no account.
- Does it work with hydrates and complex ions?
- Yes: write CuSO4·5H2O, K4[Fe(CN)6] or SO4^2- and the app reads the coefficient, the brackets and the charge.
More chemistry calculators.
Try it on your iPhone.
Free on the App Store for iPhone, iPad, Mac and Apple Watch.