Tire Pressure Temperature Calculator
Tire pressure by temperature in °F or °C: the new gauge reading in PSI, kPa or bar, or the cold pressure to set for a target. 32 PSI at 70°F reads 30.2 at 50°F. How it works
Use the Tire Pressure Temperature Calculator
About the Tire Pressure Temperature Calculator
Tire pressure drops about 1 PSI for every 10 °F of cooling. A tire set to 35 PSI at 70 °F reads 33.1 PSI at 50 °F and 30.3 PSI at 20 °F. The calculator applies Gay-Lussac's law to absolute pressure, P₂ = (P₁ + 14.696) × T₂ ÷ T₁ − 14.696 with the temperatures in kelvin, and gives the new gauge reading in PSI, kPa or bar. It also works the other way: for 32 PSI on a 50 °F morning, fill to 33.8 PSI in a 70 °F garage.
A 35 PSI tire set at 70 °F, at other outside temperatures
| Outside temperature | Gauge reading | Change | In bar |
|---|---|---|---|
| 100 °F | 37.8 PSI | +2.8 PSI | 2.61 bar |
| 90 °F | 36.9 PSI | +1.9 PSI | 2.54 bar |
| 80 °F | 35.9 PSI | +0.9 PSI | 2.48 bar |
| 60 °F | 34.1 PSI | -0.9 PSI | 2.35 bar |
| 50 °F | 33.1 PSI | -1.9 PSI | 2.28 bar |
| 40 °F | 32.2 PSI | -2.8 PSI | 2.22 bar |
| 30 °F | 31.2 PSI | -3.8 PSI | 2.15 bar |
| 20 °F | 30.3 PSI | -4.7 PSI | 2.09 bar |
| 10 °F | 29.4 PSI | -5.6 PSI | 2.03 bar |
| 0 °F | 28.4 PSI | -6.6 PSI | 1.96 bar |
| -10 °F | 27.5 PSI | -7.5 PSI | 1.90 bar |
| -20 °F | 26.6 PSI | -8.4 PSI | 1.83 bar |
Outside air temperature only, with the tire volume held fixed. Heat from driving raises the reading further, which the calculator does not model.
Frequently asked questions
- How much does tire pressure drop in cold weather?
- About 1 PSI for every 10 °F. Tires set to 35 PSI at 70 °F read 30.3 PSI on a 20 °F morning, 4.7 PSI lower, and 26.6 PSI at −20 °F. Tires at 32 PSI in a 70 °F garage read 30.2 PSI at 50 °F.
- Why does my tire read higher in the garage than outside?
- Warmer air in the tire pushes harder. A tire set to 35 PSI outside at 20 °F reads 40.2 PSI once it warms to 70 °F in the garage, with no air added. Set the pressure for the temperature the car will be driven in, with the tires cold. To fill in a warm garage for a cold morning, choose Set the cold pressure for a target pressure: for 32 PSI at 50 °F, fill to 33.8 PSI at 70 °F.
- Should I use the pressure on the tire sidewall?
- No. Michelin says the sidewall number is the most the tire can handle, not the pressure for your vehicle. The right pressure is on the placard on the driver's door jamb or inside the fuel filler flap, and it is a cold pressure. The calculator only predicts how a reading moves with temperature; compare the result with your placard.
- Why does the formula add 14.696?
- A tire gauge reads pressure above the atmosphere, but the gas law works on total (absolute) pressure. The calculator adds one standard atmosphere, 14.696 PSI, scales by the ratio of the kelvin temperatures, then takes the atmosphere off again. Scaling the gauge reading alone would understate the change.
- Can I enter the pressure in kPa or bar?
- Yes. Pick PSI, kPa or bar next to the pressure, and the number you typed is converted: 32 PSI becomes 220.6 kPa or 2.206 bar. The result is in the same unit, with kPa and bar also shown. The temperatures can be in °F or °C.
- Can I enter the temperatures in Celsius?
- Yes. Set Temperature unit to °C. Switching converts the temperatures already typed, so 70 °F becomes 21.1 °C, and the calculation runs in kelvin either way. A tire set to 32 PSI at 20 °C reads 28.8 PSI at 0 °C.
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