Ideal Gas Law Calculator

Solve for

Pressure, kPa

Volume, l

Amount of substance, mol

Temperature, °C

Result

Result22.414
What was calculatedVolume, l
Molar volume, l/mol22.414
Temperature, K273.15
Pressure, atm1
What mattersThe equation is exact for an ideal gas; real gases deviate at high pressure and near condensation.

A mole takes 22.4 litres — but not always

Solves the ideal gas law PV = nRT for pressure, volume, amount of substance or temperature, and gives the molar volume at those conditions.

PV = nRT ties four quantities together through the gas constant, 8.314 joules per mole per kelvin. Know any three and the fourth follows uniquely.

The famous 22.4 litres per mole is not a constant but a special case: the volume of one mole at zero degrees and 101.325 kilopascals. At twenty degrees the same mole takes 24 litres, and the textbook figure stops working.

What this calculator shows

Any of the four quantities in the equation
The molar volume at the conditions given
Pressure in atmospheres and temperature in kelvin

What to keep in mind

Temperature is always converted to kelvin: the equation only works on an absolute scale.
The ideal gas model ignores molecular volume and attraction, so deviation grows at high pressure and near condensation.

FAQs

What is the gas constant?

8.314462618 joules per mole per kelvin. With pressure in kilopascals and volume in litres it is used in exactly that form.

Why does one mole of gas take 22.4 litres?

That is the volume at 0 °C and 101.325 kPa. At the standard 25 °C the same mole takes 24.47 litres.

Why convert temperature to kelvin?

Because the equation is linear in absolute temperature. Zero on the Celsius scale does not mean the absence of thermal motion, and the formula would break.

How accurate is it for real gases?

For dilute gases at ordinary conditions, within a percent. Near condensation and at high pressure, real gases deviate noticeably.

Worked example

Standard conditions

Input: 1 mole, 101.325 kPa, 0 °C

Output: 22.414 litres

Note: The textbook 22.4 litres. Raise the temperature to a room-like twenty degrees and the volume climbs to 24.06 litres — almost eight percent more.

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Ideal Gas Law Calculator

Result

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