Tire Size Calculator

Inputs

View results
First number in the old tire size, such as 225 in 225/45R17.
mm
Sidewall height as a percentage of section width.
%
Wheel rim diameter in inches.
in
First number in the new tire size.
mm
New sidewall height as a percentage of section width.
%
New wheel rim diameter in inches.
in
Speed shown on the speedometer with the original tire size.
km/h

Results

Default result
Edit inputs
New tire diameter
653.2 mm
Pass

Also computed

Diameter change Pass 2.98 %

Within the common +/-3% speedometer screening range.

True speed 103 km/h

At the entered indicated speed.

Speedometer change 2.98 %

Old tire diameter 634.3 mm

New circumference 2,052 mm

Revolutions per kilometre 487.3 rev/km

Method notes 2 notes
  • Tire notation is handled conventionally: width in mm, aspect ratio in percent, and rim diameter in inches.
  • Actual rolling radius varies with tire model, load, inflation pressure, tread depth and speed. Use manufacturer data for final gearing or calibration work.

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