Enter three of pressure, volume, amount of substance and temperature to find the fourth with the ideal gas equation PV = nRT.
Last updated: November 8, 2026
The equation PV = nRT
The ideal gas law links the pressure (P), volume (V), amount (n) and absolute temperature (T) of a gas: • P × V = n × R × T • R = 8.314 J/(mol·K) = 8.314 kPa·L/(mol·K) Example: 1 mol of gas at 0 °C (273.15 K) in 22.414 L has a pressure of 1 × 8.314 × 273.15 ÷ 22.414 ≈ 101.3 kPa, which is 1 atm. Always enter the temperature in kelvin. The law is a good approximation for real gases at low pressure and high temperature; at high pressure the van der Waals equation is more accurate.
Common questions about the ideal gas law
8.314 J/(mol·K). The same number works with kPa and litres, because 1 kPa·L = 1 J.
Other tools you may find useful
In litres.
In moles.
Kelvin: °C + 273.15.