Ideal Gas Law Calculator
Solve the ideal gas law for pressure, volume, moles or temperature.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
The ideal gas law, PV equals nRT, links four quantities so that specifying three determines the fourth. Using kPa with litres and kelvin makes the gas constant exactly 8.314, which avoids the unit errors that plague this calculation.
Worked example
calculated with the default values below
Solve for Pressure · Pressure 101.325 kPa · Volume 22.414 L · Amount of gas 1 mol · Temperature 0 °C Pressure 101.3249 kPa · Volume 22.4140 L · Amount of gas 1.00000 mol · Temperature 273.15 K · Temperature 0.00 °C · Molar volume 22.4140 L/mol · Gas constant used R = 8.314 J/(mol·K) with kPa, L and K
Method and assumptions
Formula basis and scope
PV = nRT with R = 8.314462618, pressure in kPa, volume in L and temperature in K; Celsius is converted by adding 273.15.
Ideal-gas approximation only; pressure must be absolute. It does not model real-gas compressibility, phase changes or a pressure gauge offset. Singular divisors return the implementation’s fallback zero, not a physical solution.
Data sources
Disclaimer
These calculators give general conversion results. Rounding and the precision of the value you enter both affect the output, so treat displayed decimals as indicative rather than exact.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
P × V = n × R × Tk ; Tk = t + 273.15 ; R = 8.314
- P
- pressure (kPa)
- V
- volume (L)
- n
- amount of substance (mol)
- t
- temperature (°C)
Rearrange PV = nRT to solve the selected variable; molar volume = V ÷ n. Units: kPa, L, K.
Frequently asked questions
Why does the calculator use 8.314 and expect temperatures in kelvin?
The tool keeps the gas constant at 8.314 joules per mole kelvin and requires temperature in kelvin, adding 273.15 to your Celsius input, so the default 101.325 kilopascal, 22.414 litre and 1 mole at 0 degrees Celsius reproduce one mole at standard conditions. Solving for any of pressure, volume, moles or temperature rearranges PV equals nRT while the molar volume output shows litres per mole, and the constant is stated explicitly because mixing units silently breaks the equation.