Tire Calculator [AppStore, Free]

This is a useful application for driverswho want to do wheel and tire upgrades. This application will tell you in both standart and metric results:

• Sidewall Height
• Wheel&Tire Radius
• Wheel&Tire Diameter
• Tire Circumference
• Rotations per mile or kilometer
• Difference in Speedometer Readings
• And approximate Speedometer Results

And the best news is that it is now free (down from $1.99). AppStore link.

UPDATE: The price raised to $1.99