Tire Pressure Temperature Calculator

Roughly one psi for every ten degrees Fahrenheit for a typical passenger tire near 32 psi. Pressure falls as it gets colder and rises as it gets warmer, following Gay-Lussac's gas law. The exact amount scales with your starting pressure, so a higher-pressure truck tire moves a little more per degree.

Gas laws only hold on absolute scales that start at absolute zero. Fahrenheit temperatures are converted to Rankine by adding 459.67, and gauge psi is converted to absolute by adding 14.7 for sea-level atmospheric pressure. The ratio is applied there, then 14.7 is subtracted to hand you back a normal gauge reading.

Yes. Flip the unit toggle to C and both temperature fields switch, converting any values you already typed. Behind the scenes the tool still converts to Fahrenheit before running the physics, so the result is identical whichever unit you pick.

If the predicted pressure drops below the cold value on your door jamb placard, top it up to that number. Always set and check pressures when the tires are cold, meaning parked at least a few hours and not warmed by recent driving or direct sun.

Yes. Rolling friction heats the tire and can raise pressure by several psi within a few miles, which is exactly the effect this tool models. That is why the placard number is a cold spec and why you should not bleed air out of hot tires to reach it.

Final absolute pressure equals initial absolute pressure times final absolute temperature divided by initial absolute temperature. In symbols, (P1 + 14.7) times (Tf + 459.67) divided by (Ti + 459.67), then subtract 14.7 to return to gauge psi.

No. The tool assumes a fixed 14.7 psi atmospheric offset, which suits most driving. At high elevation the true atmospheric pressure is lower, so readings shift slightly, but the change in pressure across a temperature swing stays very close.

The one-per-ten rule is a linear shortcut, while the real relationship is a ratio of absolute temperatures. Near normal driving pressures and temperatures the two agree closely, but over a wide swing or at unusual pressures the exact ratio pulls away from the rule of thumb.

Yes. The calculation runs entirely in your browser with no numbers sent to a server, so nothing you type is stored or uploaded. You can use it offline once the page has loaded.