Did your TPMS light come on during the first cold morning of the year? Tire pressure drops as the air gets colder, even when nothing is wrong with your tires. Use this free tire pressure temperature calculator to see exactly how much pressure you lose (or gain) when the temperature changes, and how much air to add in a warm garage so your tires are right when you drive out into the cold.
How to Use the Calculator
- Choose Temperature change to see what happens to your current pressure when the weather changes, or Fill for cold weather to find out how much air to put in while you are in a warm garage or shop.
- Enter your pressure in psi (or switch to kPa or bar) and the temperatures in °F or °C.
- Add your recommended pressure from the sticker inside the driver’s door jamb to see whether your TPMS warning light is likely to come on.
- Use the chart and table to see the pressure at every temperature from 100°F down to −20°F.
How Much Does Tire Pressure Drop in Cold Weather?
The rule of thumb is that tire pressure changes by about 1 psi for every 10°F change in air temperature. The calculator uses the exact physics, so the numbers are slightly more precise. For a tire set to 35 psi at 70°F:
| Outside temperature | Tire pressure | Change |
|---|---|---|
| 100°F | 37.8 psi | +2.8 psi |
| 70°F | 35.0 psi | – |
| 40°F | 32.2 psi | −2.8 psi |
| 20°F | 30.3 psi | −4.7 psi |
| 0°F | 28.4 psi | −6.6 psi |
A swing from a mild fall afternoon to a freezing winter morning can easily cost you 5 psi or more, which is why so many drivers see their tire pressure light come on the first cold week of the year. We explain that in detail in why your tire pressure light comes on when it is cold.
Why Temperature Changes Tire Pressure
The air inside your tire behaves like any gas trapped in a container: when it cools, the molecules slow down and press less on the inside of the tire, so pressure falls. When it warms up, pressure rises. Because the tire’s volume barely changes, the pressure follows the temperature in a straight line.
One detail many simple calculators miss: the math has to use absolute pressure (your gauge reading plus about 14.7 psi of atmospheric pressure) and absolute temperature. This calculator does that, which is why a tire at a higher pressure loses slightly more psi per degree than one at a lower pressure.
How to Set Tire Pressure in a Warm Garage in Winter
Your door placard pressure is a cold pressure, measured at the temperature you actually drive in. If you fill your tires inside a 65°F garage and then drive out into 20°F weather, they will settle well below the placard number.
Example: your placard says 35 psi, your garage is 65°F and it is 20°F outside. The Fill for cold weather mode tells you to fill to about 39.7 psi in the garage. Once the tires cool outside, they will read 35 psi. Never inflate above the maximum pressure printed on the tire sidewall.
Cold vs. Hot Tire Pressure
- Check tires cold: before driving, or after the car has been parked for at least three hours. Driving even a few miles warms the tires and raises the reading.
- Do not let air out of hot tires. A higher reading right after a highway drive is normal. Letting air out leaves them under-inflated once they cool.
- Sun matters too. A tire in direct summer sun can read higher than one in the shade, so check all four in the same conditions.
Not sure what your number should be? Our tire PSI guide explains placard pressure vs. maximum pressure, and you can find places to check your tire pressure for free.
When Will the TPMS Light Come On?
In the U.S., tire pressure monitoring systems on newer vehicles are required to warn you when a tire is 25% or more below the recommended pressure. On a 35 psi tire, that is about 26 psi. Enter your placard pressure in the calculator and it will flag when a temperature drop gets close to that point. Learn more about tire safety from the NHTSA tire safety page.
Why Correct Pressure Matters
- Safety: under-inflated tires flex more, build up heat and grip less in wet and snowy conditions.
- Fuel economy: low pressure increases rolling resistance. The U.S. Department of Energy lists proper inflation among its tips to keep your fuel economy up.
- Tire life: running low wears the shoulders faster, while over-inflation wears the center. Our tire maintenance checklist covers the rest.
Frequently Asked Questions
Should I add air when it gets cold?
Yes. When temperatures drop for the season, check your tires cold in the morning and top them up to the placard pressure. If you fill in a warm garage, use the Fill for cold weather mode so they are correct once they cool down.
Will the pressure go back up when it gets warmer?
Yes. The change is reversible, so a tire that lost 5 psi on a cold morning gains it back as the day warms up. That is why you should check and adjust in the conditions you drive in most.
Does nitrogen stop pressure changes in cold weather?
No. Nitrogen responds to temperature almost exactly like regular air, so a nitrogen-filled tire still loses roughly 1 psi per 10°F. Its main benefit is a slightly slower leak-down over time.
Is it OK to drive with the TPMS light on in winter?
Drive gently to the nearest air pump and fill to the placard pressure. If the light comes back after you have inflated all four tires correctly, you may have a slow leak worth getting checked. Before winter, it is also worth reading how winter tires work.
Changing tire sizes as well? Compare sizes with our tire size calculator, or read more from the U.S. Tire Manufacturers Association.