Ideal gas law calculator (PV = nRT)
Choose the unknown and enter the other three values with their units. The exact gas constant R = 8.31446261815324 J/(mol·K) is used.
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How to use it
- Enter solve for, pressure p, pressure unit, volume v, volume unit and amount n.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
P × V = n × R × T with P in pascals, V in cubic meters and T in kelvin; the answer is converted to the unit you chose.
Example
Inputs: Solve for = Volume V, Pressure P = 101.325, Pressure unit = kilopascal (kPa), Volume unit = liters (L), Amount n = 1 mol. Result: Volume V: 22.41397 L; Volume in cubic meters: 0.02241397 m³.
Limits and caveats
- Real gases follow it well at low pressure and moderate temperature, less so near condensation or at high pressure.
- Torr is taken as 101325 ÷ 760 Pa; the conventional mmHg differs by less than 0.00002%.
Questions about this tool
What volume does one mole of gas take at STP?
About 22.414 L at 0 °C and 1 atm, or about 22.711 L at 0 °C and 100 kPa.
Why must temperature be in kelvin?
The law needs absolute temperature. The tool converts from °C or °F for you.
Which value of R is used?
R = 8.31446261815324 J/(mol·K), exact in the SI since 2019, which is about 0.082057 L·atm/(mol·K).