Ideal Gas Law Calculator (PV = nRT)
Solve PV = nRT for pressure, volume, moles or temperature in kPa, atm, bar, psi, L, m³, °C, °F or K with the CODATA R, plus molar volume, gas mass and density.
The missing one of P, V, n and T in the unit you chose, the same pressure and volume in every other unit, and the gas’s mass and density if you give its molar mass.
Example: One mole at 0 °C and 101.325 kPa occupies 22.414 L. Two moles in 10 L at 25 °C exert 495.8 kPa (4.893 atm); if the gas is O₂ at 32 g/mol that is 64 g at 6.4 g/L.
Four quantities,
one constant.
The equation, the value of R and where it comes from, the unit handling, and what “ideal” leaves out.
PV = nRT
Pressure × volume = amount × R × absolute temperature. Leave one of the four blank and the page solves for it. Everything is converted to SI first — pascals, cubic metres, kelvin — so R is used once, as 8.314 462 618 J mol⁻¹ K⁻¹: since the 2019 SI redefinition this is an exact value, the product of the Boltzmann and Avogadro constants (CODATA 2018). Temperature in °C or °F is converted to kelvin; a value at or below absolute zero is refused.
Units and extras
Pressure accepts Pa, kPa, bar, atm, mmHg and psi; volume L, mL, m³, cm³ and ft³, with the exact NIST factors (1 atm = 101 325 Pa, 1 psi = 6 894.757 Pa, 1 ft³ = 0.028 316 8 m³). The result is shown in every unit at once. Molar volume V/n is reported — 22.414 L at 0 °C and 1 atm, or 22.711 L at the IUPAC standard 100 kPa — and, if you give the gas's molar mass, its mass and density follow from m = nM.
What “ideal” means
The equation treats molecules as points with no attraction. Real gases depart from it at high pressure and near their boiling point; the corrections (van der Waals, compressibility factor) are not applied here and the page says so on every result. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- CODATA 2018 recommended values — molar gas constant R = 8.314 462 618 J mol⁻¹ K⁻¹ (exact)
- NIST SP 811 — pressure and volume unit factors (atm, bar, mmHg, psi, ft³)
Last reviewed 19 September 2026. How results are checked: How we verify.