BUILT FOR THE DRIVE. AND EVERYTHING AFTER.THE ENTHUSIAST’S FIELD GUIDE +
GEARLINE↗
Tools
GEARLINE TOOLS / 01

A different size.
See the difference.

Compare two tire sizes before planning your next setup.

GEARLINE TOOL GUIDE

How to compare tire sizes

Use the three numbers on each tire sidewall to compare nominal dimensions and estimate the speedometer change.

  1. 01

    Enter the original size

    For 215/45 R17, enter 215 for width, 45 for aspect ratio, and 17 for rim diameter.

  2. 02

    Enter the proposed size

    Add the replacement size using the same format. Use Swap sizes if you want to reverse the comparison.

  3. 03

    Set an indicated speed

    Choose a speed to estimate how fast the car would travel if the speedometer remained calibrated to the original diameter.

READING THE RESULT

The percentage is the change in overall diameter. The table compares nominal sidewall, diameter, and circumference. Estimated actual speed scales by the diameter ratio.

WHAT IT DOES NOT DO

This calculation does not confirm vehicle fitment, wheel width, brake or body clearance, load capacity, or safe installation. Verify the complete setup with the manufacturers and your installer.

Your tire sizes

Read the three numbers from your tire sidewall.

Original size
215/45 R17
Proposed size
225/45 R17

The default sizes are a mathematical example, not a fitment recommendation.

The difference

+1.44%overall diameter increase
OriginalProposed
Nominal tire dimensions
MeasurementOriginalProposed
Diameter625.3 mm634.3 mm
Sidewall96.8 mm101.3 mm
Circumference1964.4 mm1992.7 mm
At an indicated 60 mph60.9 mph estimated actual

Assumes the speedometer is calibrated to the original size.

Geometry, without the guesswork.

Sidewall = width × aspect ratio ÷ 100. Diameter = rim × 25.4 + twice the sidewall. Circumference = π × diameter. Estimated speed scales with the ratio of the two diameters.

These are nominal, unloaded dimensions. Actual tires vary by model, pressure, load, and wear. The result does not confirm wheel or tire compatibility, brake clearance, body clearance, load capacity, or safe installation. Verify the complete setup with the vehicle and tire manufacturers and your installer.

Understand wheel offset