Tire Pressure by Temperature Calculator

Air, like all gases, contracts when cooled. The ideal gas law (P1/T1 = P2/T2 at constant volume) means that a 50°F drop in temperature (e.g., from 70°F to 20°F) reduces absolute pressure by about 9%, which translates to roughly 4-5 psi on a typical 35 psi tire. This is purely temperature-driven - no air escapes.

Add air to the specified cold pressure from your door-jamb sticker. Check all four tires (and the spare if it has a sensor). The light usually turns off within a mile of driving once the car re-reads sensor values. If the light stays on after adding air, one tire may have a slow leak that requires inspection.

Not in principle - inflate to the placard pressure (cold). The placard pressure already accounts for all normal conditions. However, if you are in a very cold climate and must park outdoors, you may check pressure in the cold and add air to reach the placard value. Avoid checking pressure after driving when tires are hot.

Once a month is the standard recommendation, and before any long trip. TPMS only alerts you when pressure is significantly low (typically 25% below placard), which can already affect safety and fuel economy. Manual checks with an accurate gauge catch smaller issues earlier. Check in the morning before driving for the most accurate cold reading.