Tire Pressure Temperature Calculator

Air in a sealed tire behaves like a gas at roughly constant volume, so its pressure rises and falls with temperature. As the air warms, its molecules move faster and push harder on the tire walls, raising the pressure. As it cools, pressure drops. This is described by Gay-Lussac's law, which states that for a fixed mass and volume of gas, absolute pressure is proportional to absolute temperature.

A common guideline is that tire pressure changes by roughly 1 psi for every 10 degrees Fahrenheit (about 5.6 degrees Celsius) change in temperature. This is an approximation of Gay-Lussac's law around typical tire pressures and ambient temperatures. This calculator computes the exact result for your specific starting pressure and temperatures rather than using the rule of thumb.

Gay-Lussac's law states P1 divided by T1 equals P2 divided by T2, where pressures and temperatures are absolute. The new gauge pressure is found by converting the starting gauge pressure to absolute (adding atmospheric pressure), converting both temperatures to an absolute scale, scaling by the temperature ratio, then converting back to gauge pressure. This calculator handles those conversions for you.

Yes. Vehicle manufacturers specify the recommended pressure for cold tires, meaning before driving or at least three hours after, because driving heats the tires and temporarily raises the pressure. Setting pressure when tires are warm leads to under-inflation once they cool. Always check and adjust against the placard value when the tires are cold.