Home › Calculator

Tire size calculator

Pick your current size and the size you are considering. The calculator shows both tires in inches and how far off your speedometer would read.

How tire sizes are calculated

A metric size such as 265/70R17 gives the section width in millimetres (265), the sidewall height as a percentage of that width (70%) and the wheel diameter in inches (17). Sidewall = 265 × 0.70 = 185.5 mm (7.30"). Overall height = 17 + 2 × 7.30 = 31.6". See our methodology.