Ideal Gas Law Calculator
Fill in three of pressure, volume, moles and temperature, and leave one blank.
This result is an estimate only. Double-check important figures before relying on them.
How it is calculated
- PV = nRT with R = 8.314462618 kPa·L ÷ (mol·K)
- Temperature in kelvin = °C + 273.15
- The calculator rearranges the formula for the value you leave blank
To convert pressure units, use the pressure converter.
Worked example
1 mol of gas at 0 °C and 101.325 kPa:
- V = nRT ÷ P = 22.414 L, the molar volume at standard temperature and pressure
Why your number may differ
Real gases are not ideal, especially at high pressure. Some books use 0 °C and 100 kPa for standard conditions, giving 22.711 L.
Frequently asked questions
What is the ideal gas law?
PV = nRT, where P is pressure, V volume, n the amount of gas in moles, R the gas constant and T the absolute temperature in kelvin.
Which units does it use?
Pressure in kPa, volume in litres and temperature in °C (converted to kelvin inside). With these, R is 8.314 kPa·L/(mol·K).
When does the law work well?
For gases at moderate pressures and well above their boiling point. At high pressure or low temperature real gases depart from it.