🌡️ Tire Pressure Temperature Calculator
Enter your set pressure and the temperature when you set it versus now to see the current pressure.
Pressure now
29.4 psi
Change
-2.6 psi
colder → top up
Tire pressure follows Gay-Lussac\'s law: for a fixed volume of air, pressure rises and falls with absolute temperature. As a rule of thumb it changes about 1 psi for every 10 °F (roughly 0.07 bar per 5 °C). A cold snap drops your pressure — so check and top up, since low pressure hurts handling, wear and fuel economy. Always set pressure on cold tires. 🔒 In your browser.
How the tire pressure temperature calculator works
The air in a tire is a fixed volume, so by Gay-Lussac's law its pressure rises and falls with absolute temperature. The tool converts your gauge pressure to absolute, scales it by the ratio of absolute temperatures (°F converted to the Rankine scale), and converts back — giving the pressure now. The handy rule of thumb that falls out is about 1 psi of change for every 10 °F (roughly 0.07 bar per 5 °C).
Always set tire pressure when the tires are cold (before driving), because driving heats them and raises the reading by several psi. A seasonal temperature drop is why the low-pressure warning light often comes on during the first cold morning of autumn — the air genuinely contracted, so top up to the placard pressure at the current temperature.
Frequently asked questions
How much does tire pressure change with temperature?
About 1 psi for every 10 °F (roughly 0.07 bar per 5 °C) change in air temperature. A 30 °F drop lowers a 32 psi tire by around 2.5–3 psi — enough to trigger a low-pressure warning.
Why does my tire pressure light come on when it gets cold?
Cold air contracts, so the pressure genuinely drops. The first cold morning of the season often takes tires below the warning threshold even with no leak. Top them up to the placard pressure at the current temperature.
Should I set tire pressure when tires are hot or cold?
Cold — before driving, or at least 3 hours after. Driving heats the tires and raises the pressure by several psi, so setting them hot leaves them under-inflated once they cool. Manufacturer placard pressures are cold values.
Does temperature affect pressure the same in bar or psi?
The physics is the same; only the units differ. The ~1 psi per 10 °F rule is about 0.07 bar per 5 °C. The tool uses the exact Gay-Lussac relation on absolute pressure and temperature, so it's accurate in either system.
Is a pressure change from temperature a problem?
It's normal, but low pressure isn't good — it worsens handling, increases wear on the tire shoulders and cuts fuel economy. Check and adjust with the seasons, and don't bleed off the extra pressure that appears when tires are hot from driving.