Estimate how gauge pressure changes with ambient temperature using Gay-Lussac’s law. °F/°C and PSI/kPa/bar — parked cold-to-hot estimate, free and private.
33.8
Estimated PSI
233
Estimated kPa
2.33
Estimated bar
+1.8
Δ PSI
34
Rule of thumb (~1 PSI / 10°F)
Models a parked tire with ambient temperature only. Does not include heat from driving. Always check pressure cold per the vehicle placard.
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Enter the cold pressure you set, the temperature it was set at, and the ambient you expect later. The result is an estimated gauge pressure in PSI, kPa, and bar. Use it when a 35 PSI fill at 40 °F will read higher on a 90 °F afternoon — before you bleed air at the gas station.
The model is P/T constant for a closed volume: gauge is converted to absolute (plus 1 atm), temperature to Rankine, then back to gauge. That is why a 10 °F swing is not exactly 1 PSI on every fill — the rule of thumb is nearby, the formula is the physics.
Set pressure and temperature units independently. A ~1 PSI per 10 °F note sits next to the calculated delta so you can sanity-check the Gay-Lussac result. Ranges keep nonsense values out (roughly 0–150 PSI equivalent and −40 to 140 °F).
No TPMS account and no upload. This estimates parked ambient change, not heat from high-speed running, altitude, or a leaking tire. Always set pressure cold to the placard; do not “correct” a hot tire down to the sticker number. Nothing is stored on a server.
Use the pressure you actually set, in PSI, kPa, or bar — not the sidewall maximum.
Start is the temperature at fill; end is the day you are checking. Switch °F and °C as needed.
End PSI/kPa/bar and Δ PSI come from Gay-Lussac. Compare to the ~1 PSI / 10 °F rule of thumb.
The door sticker is a cold spec. If the tire is hot from driving, wait or add the estimated ambient rise — do not dump air to 32 PSI on a hot afternoon.
Straight answers on privacy, limits, and how the workspace behaves.
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