Tire Pressure Temperature Calculator
Cold weather drops your tire pressure and turns on the dashboard light. Work out what your tires will read when the temperature changes.
Temperature change
- Set pressures cold, meaning parked at least three hours or driven under a mile.
- Driving warms a tire by 5 to 8 psi. Never bleed pressure out of a hot tire to hit the placard number.
- The placard pressure is for the vehicle, not the tire. The number on the sidewall is a maximum, not a target.
Why the light comes on the first cold morning
Air pressure falls with temperature. Set your tires to 35 psi on a mild 70 degree afternoon, then wake up to 20 degrees, and they read closer to 30. Nothing leaked. The air just got colder.
TPMS in the US warns at 25% below the placard pressure. On a 35 psi placard that trips at about 26 psi, which a big enough overnight drop will reach on tires that were already a little low.
The rule of thumb, and where it comes from
Roughly 1 psi for every 10 degrees Fahrenheit. It holds well enough across normal temperatures because the underlying physics is close to linear over that range.
The actual calculation works on absolute pressure and absolute temperature, which is why the rate is not exactly 1.0 and drifts slightly depending on what pressure you started from. A tire at 50 psi shifts more per degree than one at 30.
Cold means cold
Every pressure specification for a road car is a cold pressure. Three hours parked, or less than a mile driven. Ten minutes on the highway puts 5 to 8 psi in a tire, and letting that back out leaves you badly underinflated once it cools.
Frequently asked questions
How much pressure do tires lose in cold weather?
About 1 psi for every 10 degrees Fahrenheit the temperature drops. A 50 degree swing from a warm autumn afternoon to a cold morning takes roughly 5 psi out of every tire, which is enough to trip the TPMS light on a tire that was already slightly low.
Should I overinflate in winter to compensate?
No. Set them to the placard pressure at the temperature you are actually in, and check monthly as the season changes. Deliberately running above placard shrinks the contact patch and costs you grip in exactly the conditions where you need it.
Does nitrogen stop the pressure changing?
Barely. Nitrogen follows the same gas law as air, so it loses pressure with temperature at effectively the same rate. Its real advantage is that it migrates through rubber more slowly and carries no moisture, so pressures drift less over months. It does not exempt you from checking them.
The light went off on its own. Do I still need to check?
Yes. It went off because driving warmed the tires back over the threshold, not because the pressure is correct. It will be on again tomorrow morning. Check them cold and set them properly.
Everything on this page is an estimate worked out from the numbers you entered and typical figures for the conditions you picked. Your vehicle, your parts and your conditions will differ. Check anything you intend to act on against the manufacturer's specification, the service manual, or a qualified technician. Verifying the result before relying on it is up to you.