Ideal Gas Law Calculator
Calculate pressure, volume, moles, or temperature using PV = nRT (R = 8.314 J/mol·K).
Solves for any one unknown from the three others in Pa, atm, and liters.
The Ideal Gas Law describes the relationship between pressure, volume, amount, and temperature of an ideal gas — one that perfectly follows kinetic-molecular theory with no intermolecular forces and perfectly elastic collisions.
The formula: PV = nRT
Where:
- P = Pressure (in Pascals, Pa; or atmospheres, atm)
- V = Volume (in cubic meters, m³; or liters, L)
- n = Amount of gas (in moles, mol)
- R = Universal gas constant = 8.314 J/(mol·K) or 0.08206 L·atm/(mol·K)
- T = Absolute temperature (in Kelvin, K — never use Celsius directly)
Temperature conversion: K = °C + 273.15
Solving for each variable:
- Pressure: P = nRT / V
- Volume: V = nRT / P
- Moles: n = PV / RT
- Temperature: T = PV / nR
Worked example: How many moles of oxygen fill a 10.0 L container at 2.50 atm and 25°C? T = 25 + 273.15 = 298.15 K n = PV / RT = (2.50 × 10.0) / (0.08206 × 298.15) = 25.0 / 24.46 = 1.022 moles
Real gas corrections: The ideal gas law is most accurate at:
- High temperatures (molecules have enough kinetic energy to overcome attractions)
- Low pressures (molecules are far apart)
At high pressures or near condensation, use the van der Waals equation: (P + a(n/V)²)(V − nb) = nRT
Where a corrects for intermolecular attractions and b corrects for molecular volume.
STP reference: At Standard Temperature and Pressure (0°C, 1 atm), 1 mole of ideal gas occupies 22.4 liters.