Tire pressure & temperature

Enter the measured gauge pressure and the air temperature inside the tire at that reading. Enter the final internal air temperature to estimate a warmer or cooler state. Road, outside air and tire-surface temperatures are not necessarily the internal gas temperature.

The model uses p₂ = (p₁ + pₐ) × (T₂ + 273.15) / (T₁ + 273.15) − pₐ. Pressures are gauge readings except atmospheric pressure pₐ; temperatures are in °C and converted to Kelvin. It holds volume, gas amount and atmospheric pressure constant. The default atmosphere is 1.01325 bar. The change is final minus initial gauge pressure.

The menu changes bar/kPa/psi and converts the existing pressure input; the atmosphere remains in bar. 1 bar = 100 kPa ≈ 14.5038 psi. Temperature inputs start at −273.14 °C, just above absolute zero; extreme states are mathematical illustrations, not valid real-tire conditions. Gas behavior, flexible volume, leaks, altitude changes and time-dependent warming are not modeled. Negative gauge pressure is possible mathematically, with the flexible-tire limitation shown explicitly.

This is not a tire-pressure recommendation or a command to inflate/deflate. Use the vehicle manufacturer’s cold-pressure specification; do not release air from warm tires just to match a cold specification. Sources: OpenStax: ideal gas law and Michelin: tire pressure.