Wheels & Tires
Tire Size
Decode a tire code into diameter, sidewall, circumference and revs.
Inputsdrag · tap · type
mm
%
in
Fig. 11Side and front elevation
Drawn at a fixed scale: watch the tire grow and shrink against the ground line as you move the sliders.
Overall diameter634mm
Sidewall height101mm
Circumference1,993mm
Revs per km502
Section width225mm
Rim diameter432mm
§ How it works
A metric tire code such as 225/45 R17 packs three measurements into one string, in three different units: width in millimetres, sidewall height as a percentage of that width, and rim diameter in inches.
Sidewall height
Overall diameter
There is a sidewall above and below the rim, so it counts twice. The rim is converted from inches to millimetres.
Circumference and revolutions
These are unloaded, nominal figures. Under the car's weight the tire flattens at the contact patch and the effective rolling radius is around 3 % smaller, so a real tire turns slightly more often than the nominal count.