Ideal Gas Law Calculator

The ideal gas law PV = nRT relates pressure, volume, amount and absolute temperature with R = 8.314462618 J/(mol·K); one mole at 0 °C and 101.325 kPa occupies 22.414 L.

Solve for:

Pressure PVolume VAmount nTemperature T

Absolute pressure P:

Amount of gas n:

Temperature T:

Show volume in:

Volume:

22.414 L

R = 8.314462618 J/(mol·K) (exact)
In SI: P = 101325 Pa, V = 0.022414 m³, n = 1 mol, T = 273.15 K

Ideal Gas Law

P V = n R T

P absolute pressure (Pa), V volume (m³), n amount (mol), T absolute temperature (K), R = 8.314462618 J/(mol·K)

Worked Examples

Molar volume at 0 °C, 101.325 kPa: V = 1 × 8.314462618 × 273.15 ÷ 101 325 = 22.414 L.
2 mol in a 10 L cylinder at 25 °C: P = 2 × 8.314462618 × 298.15 ÷ 0.01 = 495.79 kPa (4.958 bar).
Air in a 50 m³ room at 20 °C, 1 atm: n = 101 325 × 50 ÷ (8.314462618 × 293.15) = 2079 mol, about 60.2 kg of air (M ≈ 28.96 g/mol).

Frequently asked questions

What is the value of R?

R = 8.314462618 J/(mol·K), exact since the 2019 SI redefinition because it equals the Avogadro constant times the Boltzmann constant. In other units: 0.08205736608 L·atm/(mol·K) and 10.73159 psi·ft³/(lb-mol·°R).

What volume does 1 mol of gas occupy?

At 0 °C and 101.325 kPa, 22.414 L; at 20 °C and 101.325 kPa, 24.055 L. At the IUPAC standard of 0 °C and 100 kPa it is 22.711 L.

Why must temperature be absolute?

The law is proportional to T, so T must start at absolute zero. This calculator converts °C or °F to kelvin automatically; entering 0 °C uses 273.15 K.

When is the ideal gas law inaccurate?

At high pressure or near condensation, where molecular volume and attraction matter. Air at room temperature deviates by less than 1 % up to roughly 10 bar; use a compressibility factor Z (PV = ZnRT) for high-pressure work.

Sources

The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.

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APA

Scientific Converters. (2026, October 15). Ideal Gas Law Calculator. Retrieved October 17, 2026, from https://scientificconverters.com/calculators/ideal-gas-law/

IEEE

Scientific Converters, "Ideal Gas Law Calculator," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/calculators/ideal-gas-law/