wheel size comparison

Wheel Size Comparison

Wheel Size Comparison

Compare original and new wheel/tyre sizes, including diameter, circumference and speedometer difference.

Current Size

mm
%
in

New Size

mm
%
in
New wheel/tyre size is 0.4% smaller than current size.
Current Size 225/45 R17
New Size 235/40 R18
Diameter Difference -0.4%
Current Diameter 634.3 mm
New Diameter 631.2 mm
Difference -3.1 mm
Current Circumference 1992.6 mm
New Circumference 1982.8 mm
Speedometer Reading 70 mph = 69.7 mph

Wheel Size Comparison Calculator

Need to compare two wheel and tyre sizes quickly and accurately? Our free Wheel Size Comparison Calculator helps you check the difference between your current wheel setup and a new wheel or tyre size.

Whether you are comparing:

  • standard wheels vs upgraded wheels
  • 17 inch wheels vs 18 inch wheels
  • 18 inch wheels vs 19 inch wheels
  • different tyre widths, profiles and rim sizes

This simple online tool makes wheel and tyre size comparison fast and easy.

How to Compare Wheel and Tyre Sizes

Wheel size comparison is based on the overall tyre diameter, rolling circumference and percentage difference between the original and new setup.

Formula:

((Tyre Width × Profile ÷ 100) × 2 ÷ 25.4) + Rim Size = Overall Diameter in Inches

Wheel Size Comparison Example

If you compare a 225/45 R17 tyre with a 225/40 R18 tyre:

225/45 R17 = approximately 24.97 inches

225/40 R18 = approximately 25.09 inches

The new wheel and tyre setup is slightly larger overall.

Why Wheel Size Comparison Matters

Changing wheel and tyre sizes can affect the overall rolling diameter of your vehicle. This may influence speedometer accuracy, ride height, gearing, acceleration, fuel economy and clearance around the arches or suspension.

What Is Tyre Diameter?

Tyre diameter is the total height of the tyre from the ground to the top of the tyre. It includes the wheel rim and both tyre sidewalls.

What Is Rolling Circumference?

Rolling circumference is the distance the tyre travels in one full rotation. A larger circumference means the vehicle travels further with each wheel rotation.

Common Wheel Size Comparisons

  • 205/55 R16 vs 225/45 R17
  • 225/45 R17 vs 225/40 R18
  • 225/40 R18 vs 235/35 R19
  • 255/35 R19 vs 275/30 R20

Why Use Our Wheel Size Comparison Calculator?

  • Compare current and new wheel sizes instantly
  • Calculate tyre diameter differences
  • Check rolling circumference changes
  • Helps with wheel upgrades and tyre changes
  • Useful for cars, vans, performance vehicles and modified vehicles