Calculates tyre dimensions from the sidewall markings — e.g. 205/50/R15. Enter the three numbers from your tyre to get overall diameter, loaded radius, rolling circumference and speedo correction factor.
Tyre Markings
Enter the three numbers from your tyre sidewall. Example: 205 / 50 / R15
205
/
50
/
R15
Section width from bead to bead in millimetres
Sidewall height as a percentage of the section width
Wheel/rim diameter in inches
Results
—
Overall diameter (mm)
—
Overall diameter (in)
—
Static radius (mm)
—
Loaded radius (mm) approx.
—
Rolling circumference (mm) — used for speedo calibration
—
Sidewall height (mm)
—
Sidewall height (in)
Loaded radius is the static radius minus an approximate deflection. Low profile tyres (≤45) deflect less (~10mm) than standard profiles (~20–25mm). This is an estimate — actual deflection depends on load and pressure.