Gas Law Calculator

Apply the combined gas law to relate pressure, volume and temperature between two states.

About Gas Law Calculator

The combined gas law follows from the ideal gas law with a fixed amount of gas. Temperatures must be absolute — using Celsius gives badly wrong answers because the ratio is meaningless without a true zero. Forgetting to convert to kelvin is the most common error in gas calculations, and it produces results that can even change sign.

Formula

Gas Law

p₁V₁ ÷ T₁ = p₂V₂ ÷ T₂, with temperatures in kelvin

combined gas law: Boyle’s and Charles’s laws unified
kelvin: Absolute temperature, required for the proportionality to hold

Worked example

With the default values below, Gas Law Calculator returns Final Volume of 0.56822. Change any input above and every figure here is recalculated in your browser.

Inputs used

Initial pressureminimum 0.01 Pa: 101,325 Pa
Initial volumeminimum 0 m3: 1 m3
Initial temperatureminimum -272 C: 20 C
Final pressureminimum 0.01 Pa: 202,650 Pa
Final temperatureminimum -272 C: 60 C

Results

Final Volume: 0.56822 m3
Change in Volume: -43.18%
Initial Temperature: 293.15 K
Final Temperature: 333.15 K
Volume if Temperature Were Unchanged: 0.50000 m3

Step by step

1Values used
2Gas Law
3Final Volume= 0.56822 m3
4Change in Volume= -43.18
5Initial Temperature= 293.15 K
6Final Temperature= 333.15 K
7Volume if Temperature Were Unchanged= 0.50000 m3

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Gas Law calculated?

p₁V₁ ÷ T₁ = p₂V₂ ÷ T₂, with temperatures in kelvin The combined gas law follows from the ideal gas law with a fixed amount of gas. Temperatures must be absolute — using Celsius gives badly wrong answers because the ratio is meaningless without a true zero.

Why does Gas Law matter?

Forgetting to convert to kelvin is the most common error in gas calculations, and it produces results that can even change sign.

What values do I need to enter?

This calculator takes 5 inputs: Initial pressure, Initial volume, Initial temperature, Final pressure, Final temperature. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.