Tire Pressure Calculator Adjust pressure to maintain load capacity when changing tire sizes
Original Tire
→
New Tire
Recommended Pressure for New Tires
33 PSI
Decrease pressure by 2 PSI to maintain the same load capacity.
Original Pressure
35 PSI
2.41 bar / 241 kPa
Adjusted Pressure
33 PSI
2.28 bar / 228 kPa
Pressure Change
-2 PSI
Width Change
+10 mm
Important: This is an estimated adjustment to maintain equivalent load capacity. Always check the tire's maximum pressure rating (printed on the sidewall) and never exceed it. Consult the tire manufacturer's load/inflation tables for the most accurate recommendations.
How to Use This Calculator
Enter your original tire size and the factory-recommended pressure (found on the door jamb placard), then enter your new tire size. The calculator estimates the adjusted pressure needed to maintain equivalent load capacity.
Results are shown in PSI, bar, and kPa for universal compatibility. The adjustment accounts for changes in contact patch area due to differences in tire width and sidewall height.
Important Safety Notes
- Never exceed the maximum pressure printed on the tire sidewall.
- Always check tire pressure when tires are cold (before driving or after sitting for 3+ hours).
- Tire pressure increases approximately 1 PSI for every 10°F (5.5°C) increase in ambient temperature.
- Under-inflated tires cause excessive heat buildup, uneven wear, and increased fuel consumption.
- Over-inflated tires reduce the contact patch, causing poor traction and premature center tread wear.
Frequently Asked Questions
Yes, when you change to a different tire size, the contact patch area changes. A wider tire has a larger contact patch and can carry the same load at lower pressure. A narrower tire needs higher pressure to maintain the same load capacity. Adjusting pressure ensures even tread wear, proper handling, and safe load capacity.
Wider tires distribute load over a larger contact area, so they can run at slightly lower pressure while carrying the same weight. For example, going from 225mm to 255mm width (a 13% increase) may allow 1-3 PSI lower pressure. However, always stay within the tire manufacturer's recommended pressure range printed on the sidewall.
The manufacturer's recommended pressure for your stock tires is on a placard inside the driver's door jamb. The maximum pressure rating for any tire is on the tire sidewall. When changing tire sizes, use this calculator to estimate the adjusted pressure, then verify against the new tire's sidewall maximum. Never exceed the tire's maximum rated pressure.
For stock tires, always use the pressure on the door jamb — that's the vehicle manufacturer's recommendation for optimal handling, comfort, and fuel economy. The number on the tire sidewall is the maximum pressure the tire can safely hold, not the recommended driving pressure. When changing tire sizes, adjust from the door jamb pressure using this calculator.