Ideal Gas Law Calculator
Solve PV = nRT for any one variable. Enter the other three in whatever units you have — the calculator handles the conversions.
Temperature is converted to Kelvin and pressure/volume to atm·L internally, so any unit combination works. The ideal gas law breaks down at very high pressure or very low temperature.
How the ideal gas law works
The ideal gas law links pressure, volume, amount, and temperature for an ideal gas:
PV = nRT
Temperature must be absolute (Kelvin), and R must match your pressure and volume units — both handled here automatically. See the full ideal gas law and all chemistry formulas.
FAQ
Which value of R does this use?
Internally everything is converted to atmospheres, liters, and kelvin, then R = 0.0821 L·atm/(mol·K) is applied — so you can mix units freely (kPa with mL, °C with atm, etc.) and the result is still correct. That removes the most common ideal-gas mistake: using the wrong R for your units.
Do I have to convert temperature to Kelvin?
No — enter °C or °F and the calculator converts to Kelvin for you. The gas law only works in absolute temperature, so any Celsius/Fahrenheit input is converted before solving.
When does the ideal gas law stop working?
At very high pressure (molecules crowded together) or very low temperature (near condensation), real gases deviate from PV = nRT. Use the van der Waals equation for those conditions.