Molar Mass Calculator
Molar mass of any chemical formula — brackets, hydrates like CuSO4·5H2O and all 118 elements — with composition by mass and grams to moles.
Answer
- 10 g is
- 0.0400517 mol
- Particles (molecules or formula units)
- 2.41197 × 10²²
| Element | Atoms | Atomic weight | Mass | Share |
|---|---|---|---|---|
| Cu Copper | 1 | 63.546 | 63.546 | 25.45% |
| S Sulfur | 1 | 32.06 | 32.06 | 12.84% |
| O Oxygen | 9 | 15.999 | 143.991 | 57.67% |
| H Hydrogen | 10 | 1.008 | 10.08 | 4.04% |
- Atomic weights are IUPAC’s abridged standard values (CIAAW 2021), to five significant figures.
Compound
How is this calculated?
M = Σ (number of atoms of each element × its standard atomic weight). Moles = mass ÷ M; particles = moles × 6.02214076 × 10²³ (the Avogadro constant, exact).Runs in your browser — nothing you enter leaves this device.
About this tool
What it does
Molar Mass Calculator works out the mass of one mole of any compound from its chemical formula. Type the formula as chemists write it — H2O, Ca(OH)2, Al2(SO4)3, K4[Fe(CN)6] — including nested brackets of any kind and hydrates or adducts joined with a raised dot, a full stop or an asterisk, such as CuSO4·5H2O. It reads all 118 elements and uses IUPAC’s standard atomic weights, then shows the molar mass in grams per mole, the formula in Hill order (the order used in chemical indexes), and a table of how much of the mass each element contributes. Below that, it converts an amount: how many moles are in a mass you weighed, or how many grams make a number of moles, together with the number of molecules or formula units. If the formula has a mistake — a lower-case symbol, an unknown element, an unclosed bracket — it says exactly what and where.
How to use it
- Type a formula, or press one of the examples. Capital letters matter: Co is cobalt, CO is carbon monoxide.
- Read the molar mass, the Hill formula and the composition table.
- To convert an amount, type it and choose grams or moles; the other appears in the answer.
Limits and your data
- Atomic weights are IUPAC’s abridged standard values (CIAAW 2021), to five significant figures. Several elements’ weights vary slightly in nature; the conventional value is used, which is right for laboratory work but not for isotope studies.
- Elements with no stable isotope (technetium, promethium and everything after bismuth except thorium, protactinium and uranium) have no standard atomic weight. The mass number of the longest-lived isotope is used, shown in brackets, and the result is marked approximate.
- Charges are not part of a molar mass and are refused rather than guessed: write SO4 rather than SO4²⁻. An electron’s mass is negligible for ions.
- Condensed structural formulas such as CH3CH2OH work, but names (ethanol) and abbreviations (Me, Ph, Et) do not.
- The formula must be the exact substance you weigh: a hydrate is much heavier than the dry salt.
- Everything is worked out in your browser. The formulas you type are not sent or saved.
Questions
What is the molar mass of water?
18.015 g/mol: two hydrogen atoms (2 × 1.008) and one oxygen (15.999). Hydrogen makes up 11.19% of the mass.
How do I enter a hydrate?
Join the parts with a raised dot, a full stop or an asterisk, with the number of water molecules in front: CuSO4·5H2O, CuSO4.5H2O or CuSO4*5H2O all give 249.68 g/mol.
Is molar mass the same as molecular weight?
They have the same number. Molar mass is in grams per mole; molecular weight (relative molecular mass) has no unit. For ionic compounds such as NaCl, “formula weight” is the more correct term.
How do I convert grams to moles?
Divide the mass by the molar mass. Type the mass in Convert an amount, choose grams, and the moles appear in the answer: 10 g of CuSO4·5H2O is 0.04005 mol.