If your tire is mounted, check the sidewall to find the measurement.
ISO sizing is considered the most reliable option for measuring your tires at home. It should give you the most accurate measurement. [3] X Research source Most tires are measured using both the standard and ISO method. Additionally, their sizes should be printed on the sidewall of the tire so you can easily check them.
The ISO system includes both the bead seat diameter (BSD), as well as the width of the tire, in millimeters. As an example, a 700x35 c tire has a 622 millimeters BSD and is 35 millimeters wide, so its ISO designation would be 35-622. Similarly, a 26x2 inch tire would have a BSD of 559 mm and an ISO designation of 50-559.
If you already know the tire’s diameter and width, you can also look up the circumference on various online charts. [6] X Research source
