🌡️ Gay-Lussac's Law Calculator

How to Use This Calculator

Enter initial pressure and both temperatures in Celsius, leaving P2 blank to solve. The calculator converts to kelvin automatically.

Gay-Lussac's Law

Pressure comes from molecules hitting walls; hotter molecules hit harder and more often. Because the relationship is linear in absolute temperature, a 10 percent rise in kelvin means a 10 percent rise in pressure.

Worked Example

Aerosol can at 3 atm and 25 C (298.15 K) heated to 120 C (393.15 K): P2 = 3 x 393.15/298.15 = 3.96 atm. Nearly a full atmosphere of extra pressure from heat alone.

Safety Applications

Pressure vessels, aerosol cans, and propane tanks are all rated for maximum pressures that account for temperature swings. A propane tank left in summer sun can exceed its safe pressure even though the gas amount never changed. This is why cans carry "do not incinerate" warnings and why scuba tanks are filled slowly: compression heats the gas and raises the pressure reading temporarily.

Tires and Temperature

Tire pressure changes about 1 psi for every 10 F of temperature change. A tire filled to 35 psi in a 70 F garage reads about 31 psi on a 30 F morning, which is why tire pressure lights appear in winter. Always check pressure when tires are cold, and never bleed hot tires; the pressure will normalize as they cool.

Absolute Zero Connection

Gay-Lussac's law extrapolates to zero pressure at -273.15 C, which helped establish absolute zero. Guillaume Amontons noticed the same linear trend a century earlier. The law only holds for ideal gases; real gases liquefy before reaching zero pressure, but the extrapolation pointed physics toward thermodynamics.

Hot Air Balloons

Hot air balloons combine Charles's and Gay-Lussac's principles: heating the air raises its pressure tendency, but the open envelope lets air escape instead, lowering density so the balloon rises. Pilots control altitude by adjusting burner heat, directly manipulating the gas laws with a propane flame.