In the off road world, you often hear tires referred to as 30s, 37s, 40s, and so on. Of course, this referrs to the overall tire diameter in inches. However, many tires are sold with metric sizes, such as 265/70/16, for example. These numbers refer to tire width, sidewall height, and rim dimeter. In inches, thes tires are 31s (30.6s to be exact). So how do you convert from the metric size to the overall tire diameter?

Let's use the size 265/70/16 as example.

235 = section width of tire in millimeters (25.4mm = 1")

70 = % of section width that equals aspect height or sidewall height

16 = size of rim in inches that the tire mounts on

The formula we'll use looks like this:



So, if we're using the 265/70/16 tire size, the equation looks like this (keep in mind, the middle number is percentage, so it'll be represented as .70): :