Convert liters to moles
Volume of the gas (or liquid) you measured.
Tap a liquid in the table below to fill density and molar mass.
Honest assumptions, stated up front
The gas calculation treats your gas as ideal: accurate at everyday pressures and temperatures, unreliable very close to condensation or at tens of atmospheres. The gas type (O2, CO2, He, ...) does not change the answer, because one mole of any ideal gas occupies the same volume. For liquids there is no STP shortcut: you must supply the density and molar mass of the specific substance.
Quick reference: the liters to moles formula for a gas at STP is n = V / 22.414. This page shows how to convert liters to moles for three cases: gas at STP, gas at custom pressure and temperature, and liquids. The gas liters to moles conversion never depends on which gas you have, only on the volume and the conditions.
Worked examples
Common gases: molar mass reference
Molar mass does not affect the liters-to-moles result for gases, but you need it if you later convert moles to grams.
| Gas | Formula | Molar mass (g/mol) |
|---|---|---|
| Hydrogen | H2 | 2.016 |
| Helium | He | 4.003 |
| Methane | CH4 | 16.042 |
| Ammonia | NH3 | 17.031 |
| Water vapor | H2O | 18.015 |
| Nitrogen | N2 | 28.013 |
| Carbon monoxide | CO | 28.010 |
| Oxygen | O2 | 31.998 |
| Hydrogen sulfide | H2S | 34.081 |
| Argon | Ar | 39.948 |
| Carbon dioxide | CO2 | 44.009 |
| Nitrous oxide | N2O | 44.013 |
| Sulfur dioxide | SO2 | 64.066 |
Common liquids: tap a row to fill density and molar mass
| Liquid | Density (g/mL, 20°C) | Molar mass (g/mol) |
|---|---|---|
| Water | 0.998 | 18.015 |
| Ethanol | 0.789 | 46.068 |
| Methanol | 0.792 | 32.042 |
| Acetone | 0.784 | 58.080 |
| Hexane | 0.655 | 86.178 |
| Toluene | 0.867 | 92.141 |
| Dichloromethane | 1.326 | 84.933 |
| Glycerol | 1.261 | 92.094 |
Frequently asked questions
What is the formula to convert liters to moles?
For a gas at STP (0 degrees C, 1 atm), the formula is n = V / 22.414, where V is the volume in liters and n is the amount in moles. For any pressure and temperature, use the ideal gas law form n = PV / RT. For a liquid, use n = (V x rho) / M, where rho is the density in g/mL and M is the molar mass in g/mol.
How many liters is 1 mole of gas at STP?
At 0 degrees C and 1 atm (the chemistry-textbook definition of STP), 1 mole of an ideal gas occupies 22.414 liters. Note that IUPAC's 1982 definition uses 100 kPa instead of 1 atm, giving 22.711 liters per mole, which is why different calculators may disagree slightly.
How do I convert liters to moles at room temperature?
You cannot use the STP shortcut at room temperature. Enter your actual pressure and temperature and use n = PV / RT with R = 8.314 L-kPa/(mol-K). For example, 5.00 L of gas at 25 degrees C (298.15 K) and 101.325 kPa gives n = 0.204382 mol.
Does the type of gas matter when converting liters to moles?
In the ideal-gas model, no: equal volumes of different gases at the same pressure and temperature contain the same number of moles, so the result is identical for O2, CO2, or He. The gas type matters for liquids (density differs), for mass conversions (molar mass differs), and for real gases at high pressure or very low temperature, where the ideal approximation breaks down.
Can I convert liters of liquid to moles with this calculator?
Yes. Choose the liquid mode and enter the density (g/mL) and molar mass (g/mol) of the substance. The calculator uses n = V x 1000 x rho / M. For example, 2.50 L of water (density 0.998 g/mL, molar mass 18.015 g/mol) contains 138.496 mol.
What value of R should I use in the ideal gas law?
This calculator uses R = 8.314 L-kPa/(mol-K), with pressure in kPa, volume in liters, and temperature in kelvin. Other common forms are 0.082057 L-atm/(mol-K) and 0.083144 L-bar/(mol-K). They are the same constant in different units; using this tool, you never need to convert R yourself.
How do I convert moles back to liters?
Rearrange the same formulas: at STP, V = n x 22.414 L/mol; with custom pressure and temperature, V = nRT / P. For a liquid, V(L) = n x M / (1000 x rho).
Why do different liters-to-moles calculators give different answers?
Almost always because of different STP definitions: 0 degrees C and 1 atm gives 22.414 L/mol, while 0 degrees C and 100 kPa (IUPAC 1982) gives 22.711 L/mol, and NIST normal conditions of 20 degrees C give about 24.055 L/mol, a 1.3 percent difference at most. This tool labels its assumption (1 atm) and lets you enter your own pressure and temperature for exactness.
Can this calculator convert milliliters to moles?
Yes. Just select mL as the volume unit and the calculator divides by 1000 internally. For example, 1 mL of water (density 0.998 g/mL, molar mass 18.015 g/mol) is 0.055398 mol.
Is liters to moles the same as molarity?
No. Liters to moles converts a volume into an amount of substance (mol). Molarity (M) is a concentration: moles of solute per liter of solution. If you need concentration conversions, use a molarity calculator instead of this tool.
I have grams, not liters. Which tool should I use?
For a mass-to-moles conversion you need the molar mass, not a volume. Use a grams-to-moles calculator, which handles atomic weights and chemical formulas for you.
I have a number of atoms or molecules. How do I convert to moles?
Divide the particle count by Avogadro's number (6.02214076 x 10^23). An atoms-to-moles calculator automates this for atoms, molecules, ions, and formula units.
What are the main assumptions behind the gas calculation?
Three: the gas behaves ideally (fine at ordinary pressures and temperatures, unreliable near condensation or above tens of atmospheres), the volume is the volume of the pure gas, and the given STP shortcut assumes dry gas at 0 degrees C and 1 atm. For precise laboratory work, enter measured pressure and temperature rather than using STP.
What is the molar volume of common gases at STP?
Every ideal gas has the same molar volume at a given STP: 22.414 L/mol at 0 degrees C and 1 atm. The gases differ in mass per mole (molar mass), not in volume per mole, which is why the volume-to-moles result never asks which gas you have.
How many moles are in 10 liters of gas at 0 degrees C and 1 atm?
Using n = PV/RT: n = 101.325 x 10 / (8.314 x 273.15) = 0.446175 mol. This is the worked example the calculator verifies internally. It matches 10 / 22.414, since the STP shortcut and the ideal gas law are the same physics.
Related chemistry calculators
Scope boundary: this tool converts a measured volume in liters to moles. Particle counts belong to the atoms tool, masses to the grams tool, and concentrations to the ppm/molarity tool.
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