Tyre Pressure Calculator

What Is a Tyre Pressure Calculator?

A tyre pressure calculator is a mathematical tool for comparing a current tyre pressure with a target pressure. It calculates the difference between the two values and can convert tyre pressure between commonly used units including pounds per square inch (PSI), bar and kilopascals (kPa).

It can be useful when checking vehicle tyres, comparing pressure readings from different gauges, converting manufacturer specifications between units or determining how far a measured pressure differs from a specified target. The calculator does not determine what pressure your vehicle should use; that information should come from the vehicle manufacturer.

Why Use Tyre Pressure Calculator?

This free tyre pressure calculator provides a quick way to compare pressure readings and work with different pressure units without performing manual conversions.

How to Use Tyre Pressure Calculator

Enter the pressure you want to compare, select the appropriate units and let the calculator perform the conversion and comparison.

1. Enter the target pressure — Enter the pressure specified by your vehicle manufacturer and select whether it is given in PSI, bar or kPa.
2. Enter the current pressure — Enter the pressure currently measured in the tyre and select its unit.
3. Calculate the result — Select Calculate to compare the two pressure readings.
4. Review the conversions — View the pressure difference and the target pressure converted into PSI, bar and kPa.

How to Calculate Tyre Pressure Difference

The difference between a target tyre pressure and a current pressure is calculated by subtracting the current pressure from the target pressure. For example, if the target is 35 PSI and the current pressure is 32 PSI, the difference is 3 PSI. This means the measured pressure is 3 PSI below the target.

Tyre pressure can be expressed using different units. PSI is widely used in the UK and US, while bar and kPa are also commonly found on vehicle specifications, tyre gauges and inflation equipment. Because these units represent the same physical quantity using different scales, converting between them makes it easier to compare readings from different sources.

PSI, Bar and kPa Explained

PSI means pounds per square inch and is a unit of pressure commonly used for vehicle tyres. Bar is another pressure unit frequently used in Europe, while kPa means kilopascals and is part of the International System of Units. For reference, 1 bar is equal to 100 kPa, while 1 bar is approximately 14.5038 PSI.

Why Tyre Pressure Matters

Correct tyre inflation is important for vehicle handling, braking, tyre wear and rolling resistance. Under-inflation and over-inflation can affect how a vehicle behaves and how its tyres wear. The correct pressure varies between vehicles and can also vary according to loading conditions, so the manufacturer's specified pressure should always be used rather than a generic value.

Tyre Pressure Calculator Accuracy and Limitations

The calculations on this page use standard mathematical conversions between PSI, bar and kPa. The pressure comparison is calculated from the numerical values entered by the user. The result is therefore dependent on the accuracy of the pressure reading and the information entered into the calculator.

This calculator does not measure tyre pressure, inspect a tyre or determine whether a vehicle is safe to drive. It also does not recommend a tyre pressure. Always check the vehicle handbook, manufacturer's tyre-pressure placard or other official vehicle information for the correct pressure. Tyre pressure is normally checked when the tyres are cold, because driving can heat tyres and temporarily increase their pressure.

Frequently Asked Questions