Molar Volume Calculator
Find the molar volume of an ideal gas.
Results update as you type.
How it works
The molar volume is the volume that one mole of a gas occupies at a given temperature and pressure, and this calculator finds it for an ideal gas. You enter the absolute temperature in kelvin and the pressure in atmospheres, and it returns the molar volume in liters per mole. The value comes from the ideal gas law rearranged for one mole: molar volume equals the gas constant times temperature divided by pressure. A famous result is that at standard temperature and pressure — 0 degrees Celsius and 1 atmosphere — one mole of any ideal gas occupies about 22.4 liters, a handy number for quick gas calculations. Because temperature and pressure both appear, the molar volume increases with temperature and decreases with pressure: heating a gas expands it, while compressing it shrinks the volume per mole. Remarkably, the molar volume at given conditions is the same for all ideal gases regardless of their identity, a consequence of Avogadro's law that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. This makes molar volume useful for converting between moles and volume of gases in stoichiometry. The ideal assumption holds well at ordinary conditions. Enter the temperature and pressure to find the molar volume.
Vm = R × T ÷ P
The molar volume of an ideal gas is the gas constant times the absolute temperature divided by the pressure. Using the gas constant 0.08206 L·atm/(mol·K) with temperature in kelvin and pressure in atmospheres gives the volume one mole occupies in liters, about 22.4 liters at standard conditions.
Source:Ideal gas law
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter temperature and pressure.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Molar volume updates instantly as you type — no button to press.
Frequently asked questions
What is molar volume?
Molar volume is the volume occupied by one mole of a substance, most often referring to a gas. For an ideal gas it equals the gas constant times temperature divided by pressure. At standard temperature and pressure, one mole of any ideal gas occupies about 22.4 liters, a value widely used in gas stoichiometry calculations.
Why is molar volume the same for all ideal gases?
By Avogadro's law, equal volumes of gases at the same temperature and pressure contain equal numbers of molecules, regardless of the gas. So one mole of any ideal gas occupies the same volume under identical conditions. This is why molar volume depends only on temperature and pressure, not on the gas's identity or molar mass.
What is the molar volume at STP?
At standard temperature and pressure, defined as 0 degrees Celsius (273.15 kelvin) and 1 atmosphere, the molar volume of an ideal gas is about 22.41 liters per mole. This convenient value lets you quickly convert between moles and volume of a gas at standard conditions, a common step in chemistry problems involving gases.
How do temperature and pressure affect molar volume?
Molar volume increases with temperature and decreases with pressure. Heating a gas makes each mole occupy more space, while compressing it packs the same mole into less volume. Because both appear in the formula, you must specify the conditions when stating a molar volume; the familiar 22.4 liters applies only at standard temperature and pressure.
How is molar volume used in stoichiometry?
Molar volume converts between moles and volume of a gas, which is essential in reactions involving gases. Knowing that one mole occupies about 22.4 liters at STP lets you find how many moles a measured gas volume represents, or predict the volume of gas produced or consumed in a reaction, linking gas measurements to the mole-based equation.