Ideal Gas Law Calculator
Calculate pressure, volume, moles or temperature of a gas using the ideal gas law PV equals nRT with the gas constant.
Last reviewed by the Radiatus Cloud team
Calculate the amount of gas using the ideal gas law PV = nRT.
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Apply the ideal gas law
The ideal gas law relates the pressure, volume, amount and temperature of a gas in a single equation: pressure times volume equals the number of moles times the gas constant times the absolute temperature. This calculator uses it to find the moles of gas from pressure, volume and temperature, with the gas constant in units of litre atmospheres per mole per kelvin. At standard temperature and pressure, one atmosphere and 273.15 kelvin, 22.4 litres of gas contains one mole, a well-known benchmark the default values reproduce.
The temperature must be absolute, measured in kelvin, for the law to work correctly.
Gases and the ideal model
The ideal gas law is one of the most useful equations in chemistry and physics, accurately describing the behaviour of most gases under ordinary conditions. It combines the earlier gas laws of Boyle, Charles and Avogadro into one relationship, letting you predict how a gas responds when conditions change. Rearranging it solves for any of the four quantities.
Real gases deviate from ideal behaviour at very high pressures and very low temperatures, where molecular size and attractions matter, but for most everyday situations the ideal gas law is an excellent approximation. Remember to convert temperatures to kelvin. All calculation happens locally in your browser.
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Frequently Asked Questions
What is the ideal gas law?
It states that pressure times volume equals the number of moles times the gas constant times the absolute temperature, written PV equals nRT.
Why must temperature be in kelvin?
The law uses absolute temperature. Celsius or Fahrenheit would give wrong results, so temperatures must be converted to kelvin first.
What is the value of the gas constant?
In these units it is about 0.08206 litre atmospheres per mole per kelvin. Other unit systems use 8.314 joules per mole per kelvin.
When does the ideal gas law break down?
At very high pressures and very low temperatures, where real gases deviate because molecular volume and attractions become significant.
Can I solve for pressure or volume?
Yes. The equation rearranges to solve for any of pressure, volume, moles or temperature given the other three.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter pressure, volume and temperature to find the moles of gas.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.