Car tyre size calculator

Type the car tyre code you want to calculate in the text box, to see the results below. Type your code as it is written on your tyre, for example 195/70R15 (ISO metric tyre code) or 195/620R16 (Japanese tyre code).

Calculate tyre size

The ISO metric equivalent of

nnn/nnRnn is

nnn/nnRnn
nnnNominal width of tire in mm
nnHeight of sidewall in % of width
RR=radial
nnRim diameter code

Your tyre dimensions, metric:

  • Width (mm)
  • Height of sidewall, % of width (%)
  • Height of sidewall (mm)
  • Fits rim diameter (mm)
  • Tyre diameter (mm)
  • Rolling circumference (mm)
  • Tyre circumference (mm)
  • Rolling radius (mm)
  • Wheel radius (mm)
  • Revolutions per km

Your tyre dimensions, British/American:

  • Width (in)
  • Height of sidewall, % of width (%)
  • Height of sidewall (in)
  • Fits rim diameter (in)
  • Tyre diameter (in)
  • Rolling circumference (in)
  • Tyre circumference (in)
  • Rolling radius (in)
  • Wheel radius (in)
  • Revolutions per mile

* To calculate rolling circumference Convertworld uses the tyre dimensions at a factor of 0.96 to simulate the slight reduction of radius which occurs when a tyre is fitted to a car and meets the ground.

Tyre code explanation diagram
Tyre dimensions diagram