Tire Pressure Calculator

Start with the vehicle placard. This tool estimates the cold pressure needed for a replacement passenger tire to carry at least the original tire's estimated load. It never recommends less than the placard pressure. Verify the final setting with the tire/vehicle manufacturer or a current load-and-inflation table.

Tire Pressure Calculator

Use this calculator when changing passenger-tire size or load index. Calculate front and rear axles separately if your vehicle placard lists different pressures.

Original / OEM tire

Replacement tire

How to Use the Tire Pressure Calculator

  1. Read the original cold tire pressure from the driver's-door placard or owner's manual.
  2. Enter the original tire's load index and identify whether it is P-Metric or Euro/ISO Metric, Standard Load or Extra Load.
  3. Enter the replacement tire's load index and load class.
  4. Calculate the estimate, then confirm it against the replacement tire manufacturer's load-and-inflation data before driving.

Why Tire Pressure May Change With a Different Tire Size

A replacement tire can have a different load index or load class even when its overall diameter is similar to the original tire. Tire load capacity changes with inflation pressure, so a new tire may require a different pressure to support the same engineered load. The vehicle placard remains the starting point for the original equipment setup.

Important Safety Limits

  • Use cold pressures only; check before driving or after the vehicle has been parked long enough for the tires to cool.
  • Do not use this estimator for LT-metric, flotation light-truck, trailer, motorcycle, commercial, or specialty tires.
  • Never exceed the tire or wheel manufacturer's pressure limit.
  • Do not reduce pressure below the vehicle placard based on this calculator.
  • If the required pressure exceeds the replacement tire's load-class reference pressure, stop and verify the tire choice with a qualified tire professional.

How This Estimate Is Calculated

The estimator uses the tire load index to identify maximum load capacity, then applies a non-linear pressure-to-load relationship using a 0.585 exponent. It calculates the original tire's estimated load at the placard pressure and finds the replacement pressure needed to meet that load. Because current TRA/ETRTO tables, tire construction and vehicle requirements can differ, the result is an estimate rather than a manufacturer pressure specification.

Safety note: For an unchanged original tire size and load rating, use the vehicle manufacturer's placard pressure. The maximum pressure molded on a tire sidewall is not the normal recommended operating pressure.

Tire Pressure Calculator FAQ

Should I use the pressure on the tire sidewall?

No. For the original tire setup, use the vehicle placard or owner's manual. The sidewall marking is not the vehicle's normal recommended pressure.

Can I lower pressure if my replacement tire has a higher load index?

This calculator does not recommend going below the vehicle placard pressure. A higher load index alone is not enough to justify reducing pressure.

Does this calculator work for LT tires?

No. LT-metric and flotation light-truck tires use different load-and-inflation relationships and should be checked with the correct manufacturer or industry load table.