Ideal Gas Law Calculator

Last updated: June 2026

Find

Volume

Volume unitMoles

mol

Temperature

Temperature unit

Pressure

101,324.862 Pa

Pressure atm

1 atm

Volume litres

22.414 L

Temperature C

0 C

Formula

PV = nRT, where R = 8.314 J/(mol K). Temperatures are converted to Kelvin and volumes to cubic metres before calculation.

About this calculator

The Ideal Gas Law Calculator solves pressure, volume, moles, or temperature using PV=nRT. It is useful for chemistry and physics students comparing gas variables, STP-style examples, and questions where a gas behaves approximately ideally.

Ideal gas law

The calculator converts pressure to pascals, volume to cubic metres, and temperature to kelvin before applying PV=nRT.

PV = nRT
P = nRT / V
V = nRT / P
n = PV / RT
T = PV / nR

How to use the ideal gas law calculator

Choose the variable you need to calculate.
Enter the three known values.
Select units for pressure, volume, and temperature.
Use kelvin for direct gas-law work, or Celsius/Fahrenheit for conversion.
Review the main result and converted reference units.
Check whether your example assumes ideal behaviour.

Worked examples

One mole at STP-style conditions

Input: n = 1 mol, T = 273.15 K, V = 22.414 L

Calculation: P = nRT / V

Result: About 101,325 Pa, or 1 atm

Find moles

Input: P = 101.325 kPa, V = 10 L, T = 298.15 K

Calculation: n = PV / RT

Result: About 0.409 mol

STP vs SATP

STP and SATP use different reference temperatures and sometimes pressure conventions. Always check the convention used by your course or question.

Related gas laws

Boyle, Charles, and Gay-Lussac laws are special cases where one gas variable is held constant.

Ideal gas limitation

The ideal gas law is an approximation. Real gases can deviate at high pressure, low temperature, and near phase changes.

Frequently asked questions

What is R?

R is the gas constant. This calculator uses 8.314 J/(mol K).

Why convert temperature to kelvin?

Gas-law equations require absolute temperature.

Can I use litres?

Yes. The calculator converts litres to cubic metres internally.

When is the ideal gas law inaccurate?

It is less accurate for real gases at high pressure or low temperature.

What does n mean?

n is the amount of gas in moles.

Related calculators

boyles-law-calculator
celsius-to-fahrenheit-converter
pressure-calculator

What does this mean?

This calculator is designed to help you understand the likely number before you make a decision or start an application.

Your result should be checked against official UK guidance, especially if your circumstances include dependants, exemptions, prior leave, or a complex immigration history.

Treat the figure as a planning tool rather than legal advice. Where the answer affects an application deadline or major payment, speak to an authorised adviser.