Mole Calculator: Moles, Molar Mass, Mass, Number of Particles and Gas Volume
Work out the molar mass of a compound from its formula and convert between mass, moles, particles and gas volume.
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How this calculator works
Choose the substance from the list. For anything else pick Other and type the molar mass from your periodic table.
Choose the quantity you were given (grams, moles, particles or litres of gas) and enter its value.
The calculator gives the molar mass with the atomic masses added up, then the amount in moles, the mass, the number of particles, the gas volume and the percentage of each element by mass.
Formulas used
- n = \frac{m}{M}
- N = nN_A,\quad N_A = 6.022\times10^{23}\ \mathrm{mol^{-1}}
- V = nV_m
- \%\ \text{element} = \frac{n_{atoms}A_r}{M}\times100
Worked example
With the default numbers in the calculator above:
- Molar mass from the formula (add the atomic masses): 18.02 g/mol
- Amount of substance: 2.00 mol
- Mass: 36.03 g (0.0360 kg)
- Number of particles (atoms, molecules or formula units; Avogadro's number 6.022 x 10^23): 1.2044e+24 particles (12.04 x 10^23)
- Volume as a gas at the chosen conditions: 49.58 L
- Percentage composition by mass: H 11.19 %; O 88.81 %
Change the numbers in the calculator to see the full working, every step, for your own case.
A second worked example
A different case, with these numbers: Substance Copper(II) sulfate pentahydrate, CuSO4.5H2O; What you know The amount in moles; The value of that quantity 1.
- Molar mass from the formula (add the atomic masses): 249.68 g/mol
- Amount of substance: 1.00 mol
- Mass: 249.68 g (0.25 kg)
- Number of particles (atoms, molecules or formula units; Avogadro's number 6.022 x 10^23): 6.0221e+23 particles (6.02 x 10^23)
- Volume as a gas at the chosen conditions: 24.79 L
- Percentage composition by mass: Cu 25.45 %; S 12.84 %; O 57.67 %; H 4.04 %
Common questions
What is a mole?
A mole is the amount of a substance that contains 6.022 x 10 to the 23 particles, the same number of atoms as in 12 g of carbon-12. It lets you count atoms by weighing them.
How do I find the molar mass of a compound?
Add up the atomic masses of every atom in the formula. For water, H2O, it is 2 x 1.008 + 15.999 = 18.015 g/mol. A bracket multiplies everything inside it.
What volume does a mole of gas take up?
It depends on the temperature and pressure: 24.79 L at 25 C and 100 kPa, 22.71 L at 0 C and 100 kPa, and 22.41 L at 0 C and 101.325 kPa. Use the one your course uses.
Why does my answer differ in the last digit?
Courses use slightly different atomic masses. Keep extra digits in the working and round only the last answer.
Related calculators
Got a question about this? Ask an engineering question and get a plain-language answer with references.
Further reading: IUPAC standard atomic weights (abridged). Any first-year chemistry text on the mole concept.
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