Tire Pressure Temperature Calculator
See how a tire's pressure changes when the temperature rises or falls from when you set it.
Pressure at the new temperature
31.2 psi
Cooling from 70°F to 30°F drops about 3.8 psi — a cold snap can trip the low-pressure light.
Pressure change
−3.8 psi
Rule of thumb
≈ 1 psi / 10°F
How it works
The air in a tire follows the gas laws: heat it and the pressure climbs, cool it and the pressure falls. The handy rule of thumb is about 1 psi of change for every 10°F, which is why your tires read higher after a highway run and lower on a frosty morning.
This tool does a bit better than the rule of thumb by working in absolute terms. It adds atmospheric pressure to your gauge reading, converts both temperatures to the absolute Rankine scale, scales the pressure by the temperature ratio, and then subtracts atmospheric pressure back out to give you a gauge psi.
Enter the pressure you set, the temperature when you set it, and the temperature you want to know about. The result shows the new pressure and how many psi it moved. Because the effect is real, tire pressures are always meant to be set cold, before driving warms them up.
Frequently asked questions
Why does my TPMS light come on in winter?
A cold snap can pull several psi out of every tire. If they were near the minimum to begin with, a 20 or 30 degree drop overnight is enough to trip the low-pressure warning, even though nothing is leaking.
Should I set pressure hot or cold?
Cold, always. The pressure on your door placard is a cold spec, meaning the car has sat for a few hours or driven less than a mile. Setting it after a long drive leaves you under-inflated once the tires cool back down.
Is the 1 psi per 10°F rule accurate?
It's a close approximation for typical car pressures near room temperature. This calculator uses the full gas-law relationship instead, so it stays accurate across bigger temperature swings and higher pressures where the simple rule drifts a little.