Understand a weather-related pressure change
Estimate how the same sealed tire could read after a change in ambient temperature.
Tire Pressure Calculator
Enter measured tire pressure and two temperatures to get a constant-volume pressure-change estimate, not a recommended inflation setting.
Estimate Tire Pressure at Another Temperature
Enter a measured gauge pressure and two ambient temperatures to estimate pressure change at constant tire volume.
The temperature-adjusted pressure estimate will appear here. Always use the vehicle placard for the correct cold pressure.
How to Use Tire Pressure Calculator
1
Choose Pressure and Temperature Units
Use psi with Fahrenheit or kPa with Celsius. Switching units clears measurements to prevent reinterpretation.
2
Enter the Measured Conditions
Provide gauge pressure, measured temperature, and the temperature you want to compare.
3
Return to the Placard
Use the estimate as context, then measure cold and follow the vehicle placard.
Tire Pressure Calculator Features
- psi/°F and kPa/°C modes
- Absolute-temperature pressure calculation
- Live pressure-change estimate
- Vehicle-placard safety reminder
Common Use Cases
Interpret a warm or cold reading
Use the result as context before rechecking a cold tire against the manufacturer placard.
Limits and Important Notes
Result type: Planning estimate
Calculation Details
- Convert gauge pressure to absolute pressure.
- Convert Fahrenheit or Celsius to an absolute temperature scale.
- Apply the ideal-gas pressure ratio at constant volume.
- Convert absolute pressure back to gauge pressure.
Formula
P₂ gauge = (P₁ gauge + atmospheric pressure) × T₂ absolute ÷ T₁ absolute − atmospheric pressure
Rounding
Pressure displays to one decimal psi or kPa.
Default Assumptions
- The tire’s internal air mass and volume stay constant.
- Atmospheric pressure is approximated as 14.6959 psi at sea level.
- Measured and target temperatures represent the tire air closely enough for planning.
- Leaks, driving heat, sunlight, altitude changes, gauge error, and tire flex are excluded.
Verified Example
Inputs: 35 psi measured at 70°F, with a target temperature of 30°F.
Calculation: Convert 35 psi gauge to absolute pressure, scale by the Rankine temperature ratio, then subtract atmospheric pressure.
Result: The estimated pressure is lower; the exact output is a physics estimate, not an instruction to add or release air.
Sources and Version
Version: Constant-volume ideal-gas estimate
Last verified: 2026-08-14
Update responsibility: OnlineTool.me
- TireWise — Tire Safety Ratings and Awareness — National Highway Traffic Safety Administration (accessed 2026-08-14)
- Never use this result instead of the vehicle manufacturer’s cold inflation pressure on the door placard or owner’s manual.
- NHTSA defines cold tires as not driven for at least three hours; recheck cold after any temporary warm-tire adjustment.
- Do not use tire-sidewall maximum pressure as the vehicle’s recommended pressure.
- Damaged, leaking, overloaded, commercial, racing, aviation, or specialty tires require qualified guidance.
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