Temperature–Pressure Scenario Calculator
Model how tire pressure changes with temperature using the gas law. See psi and bar at any ambient temperature from a set point.
Model pressure changes under stated assumptions.
Temperature–Pressure Scenario Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Temperature–Pressure Scenario Calculator Works?
The Temperature Pressure Scenario Calculator works by converting gauge pressure to absolute pressure and scaling the absolute pressure by the ratio of absolute temperatures. The tool uses 4 steps.
Enter the set point
Type the pressure and temperature at inflation, for example 35 psi at 70°F (21°C).
Enter the new temperature
Type the scenario temperature, for example 20°F (−7°C).
Apply the gas law
The calculator adds 14.7 psi (1.013 bar) atmospheric pressure, converts temperatures to kelvin and scales the absolute pressure.
Read the result
The calculator returns about 30.3 psi (2.09 bar), a drop of 4.7 psi.
Temperature–Pressure Scenario Calculator Formula
The Temperature Pressure Scenario Calculator formula is P₂ = (P₁ + P_atm) × (T₂ ÷ T₁) − P_atm, with temperatures in kelvin.
P_abs = P_gauge + 14.7 psiP₂_abs = P₁_abs × T₂ ÷ T₁K = (°F − 32) × 5 ÷ 9 + 273.15≈ 1 psi per 10°F (≈ 0.07 bar per 5.6°C)- P₁, P₂
- Gauge pressure at set point and scenario
- T₁, T₂
- Absolute temperature (K)
- P_atm
- Atmospheric pressure, 14.7 psi at sea level
Worked example
A tire set to 35 psi (2.41 bar) at 70°F (21°C) drops to about 26.6 psi (1.83 bar) at −20°F (−29°C). That value sits close to the 25% drop below placard that triggers most TPMS warnings.
Temperature–Pressure Scenario Calculator Conversion Table
The Temperature Pressure Scenario Calculator conversion table models the pressure of a tire set to 35 psi at 70°F across 8 temperatures.
| Temperature | Pressure (psi) | Pressure (bar) | Change |
|---|---|---|---|
| -20°F (-29°C) | 26.6 psi | 1.83 bar | -8.4 psi |
| 0°F (-18°C) | 28.4 psi | 1.96 bar | -6.6 psi |
| 20°F (-7°C) | 30.3 psi | 2.09 bar | -4.7 psi |
| 40°F (4°C) | 32.2 psi | 2.22 bar | -2.8 psi |
| 60°F (16°C) | 34.1 psi | 2.35 bar | -0.9 psi |
| 70°F (21°C) | 35.0 psi | 2.41 bar | +0.0 psi |
| 90°F (32°C) | 36.9 psi | 2.54 bar | +1.9 psi |
| 110°F (43°C) | 38.8 psi | 2.67 bar | +3.8 psi |
The model assumes a fixed tire volume and sea-level atmospheric pressure.
What is Temperature–Pressure Scenario Calculator?
A Temperature Pressure Scenario Calculator is a tool that predicts tire pressure at a different temperature from the temperature at inflation. Gas pressure in a fixed volume rises and falls in proportion to absolute temperature.
Cold mornings trigger TPMS warnings in autumn. A garage-set tire loses about 1 psi for each 10°F (5.6°C) drop outside.
Driving heats a tire by 20 to 50°F (11 to 28°C) and raises pressure by 2 to 5 psi. Placard pressures already account for that rise, so drivers never bleed air from a hot tire.
What are the uses of Temperature–Pressure Scenario Calculator?
There are 4 main uses of the Temperature Pressure Scenario Calculator, including winter inflation and track pressure planning.
Winter inflation
Add pressure in a warm garage to reach placard pressure outside.
Track pressure planning
Estimate hot pressure from a cold set point.
TPMS warnings
Explain a morning TPMS light after a cold night.
Travel planning
Predict pressure changes on a trip to a colder or hotter region.
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