About the Tire Size Comparison Calculator
Compare two tyre sizes for diameter, width and speedometer effect before changing wheels.
Also known as: tire size difference, plus sizing calculator, compare tyre sizes, wheel upgrade calculator.
How to use this calculator
- Enter original width, original aspect, original rim, new width and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
difference % = (new diameter − old diameter) ÷ old diameter × 100
Worked example
Using the values pre-filled in the calculator above:
- Original width = 205 mm
- Original aspect = 55 %
- Original rim = 16 in
- New width = 225 mm
- New aspect = 45 %
- New rim = 17 in
the calculator returns:
- Diameter difference: 0.38 %
- Original diameter: 631.9 mm
- New diameter: 634.3 mm
- Difference: 2.4 mm