Tire Calculator (Offset&Speed)

Tire Calculator (Offset & Speed) helps you accurately compute wheel offset and speedometer error when upgrading tires or wheels. It covers offset calculations (rim width, offset, backspace) and both inner and outer rim position changes, plus tread changes, and it includes speedometer error calculations using tire size or direct outer diameter input.

In addition, you can measure speedometer error with GPS by comparing GPS speed to the vehicle speedometer. The app features an easy-to-use interface, clear results, and notes about potential brand differences, so you can plan tire changes with confidence.