This calculator requires the use of Javascript enabled and capable browsers. It is to determine helpful information about tire replacement sizes. Enter the original tire size then enter the desired replacement size, aspect ratio and wheel diameter. For informational purposes only, the following is an example to help to decode a tire size like 195/70R15. The 235 is the tire width in millimeters, measured from the bottom of the bead to the bottom of the bead, the 75 is the sidewall aspect ratio, the ratio of sidewall height to tire width at the tread (indicating that the sidewall height is 75% of the tread width), and the 15 is the wheel rim diameter in inches. Click on Calculate for the information concerning the new tire diameter compared to the original, and speedometer differences due to tire size changes to be displayed.
