Ideal Gas Law Calculator (PV = nRT)
Solve the ideal gas law for pressure, volume, moles or temperature — with unit choices for kPa, atm, bar, litres and °C, K or °F.
How to use
- 1Choose the unknown.
- 2Enter the other three values with their units.
How it's calculated
PV = nRT, with R = 8.314462618 J/(mol·K) = 0.082057 L·atm/(mol·K). Temperatures are converted to kelvin.
Frequently asked questions
What volume does one mole of gas occupy?
About 22.414 L at 0 °C and 1 atm (STP), or 24.465 L at 25 °C and 1 atm.
Why must temperature be in kelvin?
The law uses absolute temperature — 0 °C would otherwise make PV zero.
When does the ideal gas law fail?
At high pressures and low temperatures, where molecules' size and attractions matter; use the van der Waals equation then.