Gay-Lussac's Law Calculator
Pressure and temperature at constant volume.
Work out Gay-Lussac's Law. Pressure and temperature at constant volume. Free, with no account and nothing to download.
P₂
1.0682 atm
1.0682× the starting pressure
Gay-Lussac's law is where the kelvin conversion matters most, because the numbers are so misleading in Celsius. Doubling from 20 °C to 40 °C is only 293 K to 313 K — a 6.8% rise in pressure, not 100%. That is also why a sealed aerosol can in a hot car is a real hazard rather than a theoretical one: it takes a fair temperature rise to burst it, but the pressure climbs steadily and there is no relief path. The law holds at constant volume and constant amount of gas. If the container can flex, or gas escapes, it does not apply.
How the Gay-Lussac's Law Calculator works
Solve P₁/T₁ = P₂/T₂ for whichever quantity you are missing. Temperatures go in as Celsius and are converted to kelvin for you, which is the whole difficulty with this law — 20 °C to 40 °C is a 6.8% pressure rise, not the doubling that Celsius suggests.
Also known as: pressure temperature law calculator · p1/t1 = p2/t2 calculator · constant volume gas law calculator · gay lussac's law formula
Frequently asked questions
What is Gay-Lussac's law?
At constant volume, the pressure of a fixed amount of gas is proportional to its absolute temperature: P₁/T₁ = P₂/T₂.
Why must temperature be in kelvin?
Because the law is a proportionality, and proportionality needs a scale with a true zero. Celsius does not have one — 40 °C is not twice as hot as 20 °C in any physical sense, but 313 K is genuinely 1.068 times 293 K.
Why do aerosol cans warn against heat?
This law. A sealed can has fixed volume, so heating it raises pressure with no relief path. Going from 20 °C to 60 °C adds about 14% — enough to matter when the can is already pressurised and there is nowhere for the gas to go.
How is this different from Charles's law?
Charles's law holds pressure constant and relates volume to temperature. Gay-Lussac holds volume constant and relates pressure to temperature. Both are special cases of the combined gas law.
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