Ideal Gas Law Calculator
PV = nRT • Leave exactly one variable empty to solve it
Use SI for Pa + m³. Use L·atm for atm + L style solving.
Quick summary
Fill any 3 fields and leave exactly 1 empty, then click Calculate.
Leave empty if pressure is the unknown.
Leave empty if volume is the unknown.
Leave empty if amount is the unknown.
Temperature must be above absolute zero. Leave empty if temperature is the unknown.
Results
Solved variable
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Value (selected units)
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Consistency check
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Shows PV/(nRT). A valid result is usually very close to 1.
Use this Ideal Gas Law Calculator to solve for pressure, volume, amount of gas, or temperature. Enter any three values and leave the variable you want to calculate empty.
Ideal Gas Law Formula
PV = nRT
- P: absolute pressure
- V: gas volume
- n: amount of gas in moles
- R: ideal gas constant
- T: absolute temperature in kelvin
The equation can be rearranged depending on the unknown value:
- Pressure: P = nRT ÷ V
- Volume: V = nRT ÷ P
- Amount: n = PV ÷ RT
- Temperature: T = PV ÷ nR
Use R = 8.314462618 Pa·m³/(mol·K) for SI units or R = 0.082057366 L·atm/(mol·K) when pressure is in atmospheres and volume is in litres.
Worked Example
Suppose 0.5 mol of gas is at 2 atm and 300 K. Calculate its volume using the L·atm gas constant.
V = nRT ÷ P
V = (0.5 × 0.082057366 × 300) ÷ 2
V ≈ 6.15 L
The estimated gas volume is approximately 6.15 litres.
Important Notes
- Temperature must be expressed as an absolute temperature. The calculator converts Celsius and Fahrenheit to kelvin when those units are selected.
- Pressure must be absolute pressure, not gauge pressure.
- The selected pressure and volume units must be compatible with the gas constant.
- The ideal gas law is an approximation and may be less accurate at high pressures, very low temperatures, or near condensation.