Ideal Gas Law Calculator
Apply the ideal gas law PV = nRT to solve for any unknown. Enter three of the four variables (pressure, volume, temperature, moles) to find the fourth.
The Ideal Gas Law
PV = nRT
P = pressure (Pa), V = volume (m³), n = moles of gas, R = 8.314 J/(mol·K) (universal gas constant), T = absolute temperature (Kelvin). Remember: T(K) = T(°C) + 273.15. Standard conditions: STP is 0°C (273.15K) and 101,325 Pa.
Molar Volume
At STP (0°C, 1 atm), one mole of any ideal gas occupies 22.4 litres. At SATP (25°C, 100kPa), it occupies 24.8 litres. These are useful reference values for gas stoichiometry calculations.
Limitations
The ideal gas law assumes no intermolecular forces and zero particle volume — accurate for most gases at low pressure and high temperature. At high pressures or low temperatures (near condensation), real gases deviate significantly and the van der Waals equation is needed.
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