Using the Calculator
To use the calculator, select a wheel and tire size from the drop-down menus, or enter the wheel and tire size in millimeters (mm) in the corresponding fields. The calculator will then display the estimated circumference in both millimeters and centimeters.
The calculator is based on the ISO/ETRTO tire size standards. This specification defines tire size as a tire width and rim circumference in millimeters (mm). For example, an ISO tire size of 28-622 refers to a 700 x 28C tire, which has a tire width of 28 mm and a rim diameter of 622 mm.
If your wheel size is not listed in the drop-down menu, you can simply enter the number into the "Diameter (mm)" field.