Tire Pressure Temperature Calculator
See how tire pressure changes with temperature and find the adjusted psi for a new ambient temperature.
How it works
New psi ≈ current psi + (new temp − set temp) ÷ 10 (about 1 psi per 10 °F)
Air pressure tracks temperature: as the air in a tire cools it contracts and the gauge reads lower, and as it warms the pressure climbs. The well-known rule of thumb is roughly 1 psi for every 10 °F of change. That is why tires that were perfect in warm weather read low on the first cold morning, often tripping the low-pressure warning light even though nothing is leaking. This estimate assumes the tire volume is fixed and uses the practical 1-psi-per-10-°F figure rather than the exact gas law, which is close enough for setting pressures.
Worked example
A tire set to 32 psi on a 70 °F afternoon is measured on a 40 °F morning. The temperature dropped 30 °F, so the pressure falls by about 30 ÷ 10 = 3 psi, reading roughly 29 psi. Adding 3 psi brings it back to the intended 32.
Frequently asked questions
Why does my low-pressure light come on in winter?
A cold snap lowers tire pressure by about 1 psi per 10 °F. A tire set correctly in autumn can read several psi low on the first freezing morning, which is often enough to trigger the TPMS warning even with no leak.
Should I set pressure hot or cold?
Always cold — before driving or after the car has sat a few hours. Driving heats the tires and raises the pressure a few psi, so setting them hot leaves them underinflated once they cool.
Is the 1 psi per 10 °F rule exact?
It is a practical approximation of the ideal gas law that holds well over normal ambient swings. The exact figure depends on the starting pressure, but 1 psi per 10 °F is close enough for everyday tire setting.
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Educational estimate. Real-world results vary with conditions, tuning and measurement.