Why does tire pressure change with temperature?

Tire pressure follows the ideal gas law: for every 10°F (5.5°C) change in temperature, tire pressure changes by approximately 1-2 PSI. When temperature drops, air molecules move slower and take up less space, decreasing pressure. When it heats up, molecules move faster and expand, increasing pressure. This is why tire pressure is lower in winter mornings and higher in summer afternoons. Seasonal temperature changes of 40-50°F can cause pressure changes of 4-10 PSI, significantly affecting performance and safety.

What is the correct tire pressure for my car?

The recommended tire pressure is specified by your vehicle manufacturer, not the tire brand. Find it on a sticker inside the driver's door jamb, in the owner's manual, or sometimes inside the fuel door. It's listed in PSI (pounds per square inch) for cold tires and often differs between front and rear tires. Never use the 'max PSI' shown on the tire sidewall—that's the maximum the tire can handle, not the recommended pressure. Typical passenger cars use 32-35 PSI, while trucks and SUVs might use 35-45 PSI.

When should I check my tire pressure?

Check tire pressure at least monthly and before long trips. Always check when tires are cold (before driving or at least 3 hours after driving). Driving heats tires and increases pressure by 4-6 PSI, giving falsely high readings. Check more frequently during temperature changes between seasons. If your TPMS (Tire Pressure Monitoring System) warning light comes on, check pressure soon—it typically activates when pressure is 25% below recommended. Proper inflation improves fuel economy, tire lifespan, handling, and safety.

Can I slightly overinflate my tires?

A slight overinflation (1-2 PSI above recommended) is harmless and accounts for gradual air loss between checks. However, significantly overinflated tires (5+ PSI over) reduce the contact patch with the road, causing uneven wear (center wear), harsher ride, reduced traction, and increased risk of damage from potholes or debris. Underinflation is more common and more dangerous—it increases rolling resistance (worse fuel economy), heat buildup (tire failure risk), and causes edge wear. Stick within 1-2 PSI of manufacturer recommendations.

Health

Tire Pressure

Calculate recommended tire pressure for temperature.

Expected Pressure

-- PSI

Tire pressure drops by approximately 1 PSI for every 10°F drop in temperature.

How to Use This Calculator

Find Your Recommended Pressure

Locate your vehicle's recommended tire pressure on the sticker inside the driver's door jamb or in your owner's manual. Note if front and rear tires have different recommendations. This is your baseline 'cold' tire pressure at 68°F (20°C).

Enter Current Temperature

Input the current outdoor temperature or the temperature at which you'll be checking/filling your tires. For best results, check tire pressure in the morning before driving when tires are cold.

Enter Reference Temperature (Optional)

If your tire pressure was last set at a specific temperature, enter it here. Otherwise, use the standard reference of 68°F (20°C) that manufacturer recommendations assume.

View Adjusted Pressure

The calculator shows the adjusted recommended pressure for the current temperature. Use this target when inflating your tires. Remember to recheck pressure when seasons change, as a 40°F temperature swing can change pressure by 4-8 PSI.