Tire Pressure vs Temperature Calculator
Tire pressure drops when it gets cold and rises when it warms up. Enter your pressure and the temperature change to see the new pressure.
How to use the Tire Pressure vs Temperature Calculator
- Enter the tire pressure you measured.
- Enter the temperature when you measured it.
- Enter the new temperature to see the new pressure.
How it works
Air in a tire behaves like an ideal gas: absolute pressure is proportional to absolute temperature. The calculator converts gauge pressure to absolute (adding 14.7 psi), scales it by the ratio of absolute temperatures in Rankine, and converts back. The handy rule of thumb is about 1 psi per 10 °F change. That is why the tire pressure warning light often comes on during the first cold morning of autumn.
Pressure change for a tire set to 35 psi at 70 °F
| Temperature | Pressure |
|---|---|
| 0 °F (-18 °C) | 28.4 psi |
| 20 °F (-7 °C) | 30.3 psi |
| 32 °F (0 °C) | 31.4 psi |
| 50 °F (10 °C) | 33.1 psi |
| 70 °F (21 °C) | 35 psi |
| 90 °F (32 °C) | 36.9 psi |
| 110 °F (43 °C) | 38.8 psi |
Frequently asked questions
How much does tire pressure drop in cold weather?
About 1 psi for every 10 °F drop.
Should I check tire pressure hot or cold?
Cold — before driving or after the car has been parked for 3 hours.
Why is my tire light on in the morning?
Overnight cold lowers pressure; it may rise again as tires warm up, but you should top them up.
Should I inflate to the sidewall number?
No — that is the maximum. Use the pressure on the driver’s door placard.