Ideal Gas Law Calculator

Reviewed August 2026

Solve PV = nRT for pressure, volume, amount of gas or temperature, then estimate gas mass and density from a selected molar mass.

Scope: Best suited to dilute gases at moderate pressure and temperatures well above condensation. Real-gas effects may be important at high pressure or near phase boundaries.

What this calculator does

Select the unknown variable, enter the other three state variables, and the calculator solves PV = nRT. All calculations are performed internally in SI units. A molar-mass input provides corresponding gas mass and density estimates.

Inputs

Solve for

Absolute pressure kPa(a)

Volume m³

Amount of gas mol

Temperature °C

Molar mass g/mol

Dry air ≈ 28.97; nitrogen 28.01; oxygen 32.00; carbon dioxide 44.01 g/mol.

Results

Enter valid values to calculate.

Solved value—

Absolute temperature—

Gas mass—

Gas density—

Specific volume—

PV / nT check—

When the ideal-gas model works

The model is generally most useful at low to moderate gas density, where intermolecular forces and molecular volume have limited influence. Engineering screening calculations for air, nitrogen, oxygen, and similar gases near ambient conditions are typical applications.

Common mistakes

Using gauge pressure instead of absolute pressure.
Using °C or °F directly in the equation.
Applying the model near condensation or at very high pressure.
Mixing litres, cubic metres, mol, and kmol without conversion.