Ideal Gas Law Calculator
Calculate pressure, volume, moles, or temperature using the ideal gas law PV = nRT.
Supports all four solve modes.
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.