Ideal Gas Law Calculator
Enter any three of pressure, volume, moles and temperature and this calculator finds the fourth using PV = nRT. Choose convenient units and the values are converted to atm, litres and kelvin internally.
How to use the ideal gas law calculator
- Pick units for pressure, volume and temperature.
- Enter exactly three of pressure, volume, moles and temperature.
- Read the fourth value, solved from PV = nRT.
Examples
Molar volume at STP
n = 1 mol, T = 273.15 K, P = 1 atm
V = 22.414 L
Solve for pressure
n = 1 mol, T = 273.15 K, V = 22.414 L
P = 1 atm
Frequently asked questions
What is the ideal gas law?
The ideal gas law is PV = nRT, linking pressure, volume, moles and temperature through the gas constant R for an ideal gas.
What value of R does this use?
It uses R = 0.082057 L atm per mol per kelvin. Other units are converted to atm, litres and kelvin before solving.
Why must temperature be in kelvin?
The law is only valid on an absolute temperature scale. Celsius inputs are converted by adding 273.15 to get kelvin.
How many values do I need?
Exactly three of the four. From any three of pressure, volume, moles and temperature the fourth is fully determined.
Does it work for real gases?
It assumes ideal behaviour, which is accurate for many gases near room temperature and moderate pressure but less so at high pressure or low temperature.
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