Optimal Car Tire Pressure Calculator

Correct tire inflation determines the contact patch between your vehicle and the road. While the manufacturer's placard on the door jamb provides a baseline for stock tires and standard loads, it becomes inaccurate when tire specifications change or vehicle weight distribution shifts. This calculator uses the ETRTO (European Tyre and Rim Technical Organisation) calculation method to determine the specific pressure required to support a given load.

Under-inflation leads to excessive sidewall flexion, heat buildup, and eventual failure. Over-inflation reduces the contact patch, causing uneven center wear and compromised traction. This tool is particularly useful for modified vehicles, aftermarket wheel setups, or when carrying heavy cargo where the axle load differs significantly from the factory curb weight.

The calculation relies on the relationship between load capacity and internal air pressure. For standard P-metric tires, the load capacity varies with pressure according to a power law. The core equation derived from ETRTO standards is:

Where P_req is the required pressure, P_ref is the reference pressure (typically 2.5 bar for Standard Load or 2.9 bar for Extra Load), L_actual is the actual load on the tire, and L_max is the maximum load rating from the Load Index table.

For highway driving speeds exceeding 160 km/h, additional pressure is required to counteract centrifugal deformation of the tire casing.