Ideal Gas Law (PV = nRT)

Solve for any of P, V, n, T given the other three. R = 8.314 J/(mol·K).

Inputs

Result

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How to use this calculator

  • Pick what to solve for.
  • Enter the three known values.
  • Note: T in Kelvin, V in liters, P in kPa.

About this calculator

Ideal gas law: PV = nRT. Holds well for most gases at moderate pressures and temperatures (away from condensation). R = 8.314 J/(mol·K). Note: 22.4 L of any gas at STP (273.15 K, 101.325 kPa) = 1 mole — useful identity. Real gases deviate at high pressure (>10 atm) or low temp (near boiling). For more accuracy, van der Waals or Redlich-Kwong equations.

Frequently asked

STP?+
Standard Temp + Pressure: 273.15 K (0°C) and 101.325 kPa (1 atm). 1 mol gas = 22.414 L.
When does ideal fail?+
High pressure (molecules close, intermolecular forces matter), low temp (approaching condensation). Air at 1 atm, 25°C: nearly ideal.
R values?+
8.314 J/(mol·K), or 0.08206 L·atm/(mol·K). Same constant, different units.
Mole vs. mass?+
PV = nRT uses moles. For mass: PV = (m/M)RT, where M = molar mass.
Convert °C to K?+
K = °C + 273.15. Always use absolute (Kelvin) in gas laws.

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