Ideal Gas Law Calculator
Solve the Ideal Gas Law PV = nRT for any one unknown variable given the other three.
Results
What is it?
The Ideal Gas Law PV = nRT relates pressure (P), volume (V), moles (n), and absolute temperature (T) for an ideal gas. R = 8.314 J/(mol·K) is the universal gas constant. At STP (0°C, 1 atm) one mole of ideal gas occupies ~22.4 L; at SATP (25°C, 100 kPa) it occupies ~24.8 L.
How to use
Select the variable you want to solve for, then fill in the other three. All inputs must use SI units: Pascals, cubic metres, moles, and Kelvin. To convert: 1 atm = 101325 Pa; °C to K by adding 273.15; 1 litre = 0.001 m³.
Example scenario
How many moles are in a 5 L balloon at 25°C and 1 atm? Select "Moles", enter P = 101325 Pa, V = 0.005 m³, T = 298.15 K. Result: n = PV/(RT) = 101325 × 0.005 / (8.314 × 298.15) ≈ 0.204 mol.
Pro tip
Real gases deviate from ideal behaviour at high pressures and low temperatures. The van der Waals equation adds correction terms for intermolecular attractions and finite molecular volume. Boyle's Law (T constant: P₁V₁ = P₂V₂), Charles's Law (P constant: V₁/T₁ = V₂/T₂), and Gay-Lussac's Law (V constant: P₁/T₁ = P₂/T₂) are all special cases of PV = nRT.