Gay-Lussac's Law Calculator

Gay-Lussac's Law states that for a fixed amount of gas held at constant volume, the pressure is directly proportional to the absolute temperature. In equation form that is P1/T1 = P2/T2, so doubling the Kelvin temperature doubles the pressure.

The proportionality only works from absolute zero, so a scale that starts at zero is required. The calculator adds 273.15 to any Celsius value to reach Kelvin before solving, then subtracts it again to report the answer in the unit you chose.

Any unit works because only the ratio of the two pressures enters the equation. Whether you use pascals, atmospheres, psi or bar, the result is correct as long as P1 and P2 share the same unit.

Exactly three of the four. The Solve for menu marks the fourth as unknown and disables its box, and from any three of P1, T1, P2 and T2 the missing one is fully determined.

Each law holds one variable fixed. Gay-Lussac's keeps volume constant and links pressure to temperature, Boyle's keeps temperature constant and links pressure to volume, and Charles's keeps pressure constant and links volume to temperature.

The calculator rejects it. A Kelvin value of zero or less, or a Celsius value at or below minus 273.15, is physically impossible and would divide by zero or worse, so the tool shows an error instead of a number.

No. Pressure must be greater than zero, so a zero or negative entry is flagged as invalid. Temperatures in Celsius may be negative as long as they stay above minus 273.15.

It is exact for an ideal gas and a close approximation for real gases well away from their condensation point. Near very high pressures or very low temperatures, real-gas behaviour drifts from the simple proportion.

No. The algebra runs in your browser the moment you change an input, so your numbers are never sent anywhere and results appear instantly.