Tire Size Comparison Calculator

By AutomotiveCalc · Full tool, formula & sources

Nominal dimensions only. This tool does not confirm safe tire fitment or compatibility.

Your numbers

Example calculation

Example results are shown below. Controls become available when the calculator loads.

Have a size code? Apply it here, or edit the dimensions below. Supports metric radial sizes such as 225/45R17. Size codes do not confirm vehicle fitment. How to read tire sizes →

Paste original tire size (optional)

Paste new tire size (optional)

Original width (mm)

Original aspect ratio (%)

Original wheel diameter (inches)

New width (mm)

New aspect ratio (%)

New wheel diameter (inches)

Indicated speed (mph)

Diameter difference1.42 %

Estimated actual speed60.85 mph

Original diameter24.97 in

New diameter25.33 in

Unloaded geometry at the same scale. Dashed circles show the wheels. Actual tire dimensions can differ.

Dimensions compared
Measurement	Original	New
Diameter (mm)	634.30	643.30
Sidewall (mm)	101.25	105.75
Wheel (in)	17.00	17.00

Speedometer comparison — assuming original calibration was accurate
Indicated (mph)	Estimated actual (mph)
30.00	30.43
45.00	45.64
60.00	60.85
70.00	70.99

This comparison does not establish safe fitment, clearance, load capacity, or compatibility with vehicle electronics. Use manufacturer-approved specifications.