Ideal Gas Law Calculator (PV=nRT)

The Ideal Gas Law is one of the most fundamental equations in chemistry and physics. It describes the behaviour of an ideal gas — a theoretical gas that obeys simple rules about particle size and interaction.

The equation is:

PV = nRT

Where:

• P = Pressure (in Pascals, Pa, or atmospheres, atm)
• V = Volume (in cubic meters, m³, or litres, L)
• n = Amount of gas in moles (mol)
• R = Universal gas constant = 8.314 J/(mol·K) = 0.08206 L·atm/(mol·K)
• T = Temperature in Kelvin (K = °C + 273.15)

This equation can be rearranged to solve for any one variable if the other three are known:

• P = nRT / V
• V = nRT / P
• n = PV / RT
• T = PV / nR

Practical applications include:

• Calculating gas pressure in a sealed container after temperature changes
• Determining how much gas fits in a tank at a given pressure
• Chemistry stoichiometry for reactions involving gaseous products or reactants
• Engineering applications for pneumatics, HVAC, and thermodynamics

At standard temperature and pressure (STP: 0°C and 1 atm), one mole of any ideal gas occupies 22.4 litres. At standard ambient temperature and pressure (SATP: 25°C and 1 bar), one mole occupies about 24.5 litres.

Ideal gas assumptions break down at very high pressures (particles are too close together) and very low temperatures (particle interactions and volume become significant). Real gases like CO₂ or water vapour deviate more from ideal behaviour than simple gases like helium or hydrogen.

Temperature must always be in Kelvin for this equation. If you enter Celsius or Fahrenheit, this calculator will convert it automatically.