Enter the 1st number in the box to the right of Tire Width. The 1st number represents the tread width measured in millimeters.

Enter the 2nd number in the box to the right of Aspect Ratio. The 2nd number represents the aspect ratio of the sidewall versus the tread width displayed as a percentage.

Enter the 3rd number in the box to the right of Wheel Diameter. The 3rd number represents your wheel size.

The tire calculator will the calculate tire height and width for you in inches. For example: To convert 285/75/16, enter 285 in the Tire Width box, 75 in the Aspect Ratio Box, and 16 in the Wheel Diameter Box. Then Click on Convert Tire Size button. You may enter other sizes, clicking Convert Tire Size button after changing your numbers.