Tire Size

Compare dimensions and the speedometer effect.

Your numbers

Enter your numbers to see the result.

How Tire Size works

Sidewall height = width in millimeters × aspect ratio ÷ 100. Convert two sidewalls to inches and add rim diameter. Compare diameters and circumferences; estimated actual speed scales by new diameter divided by old diameter.

A worked example

These sample values illustrate the calculation. Use your own numbers in the calculator for your result.

Example inputs
Current width (mm)
205
Current aspect ratio (%)
55
Current wheel diameter (in)
16
New width (mm)
225
New aspect ratio (%)
45
New wheel diameter (in)
17
Indicated speed (mph)
60
Diameter difference
0.3798%
Current diameter
24.878 in
New diameter
24.9724 in
Current sidewall
112.75 mm

Assumptions and limits

Dimensions alone do not establish compatibility. Tire sizes can affect clearance, handling, load rating and vehicle systems. Confirm fitment with the manufacturer or a tire professional.

Check lender terms and manufacturer guidance. These estimates do not replace a mechanical inspection.