Tire Size Calculator
Compare two tire sizes — diameter, speedo error
Original tire (OEM)
New tire
📚 Learn more — how it works, FAQ & guide Click to expand
Learn more — how it works, FAQ & guide
Click to expand
Tire size calculator
Compare two tire sizes. Check speedo error and rubbing risk.
How to use this tool
- 1
Enter OEM tire
Format like 225/65R17. This is the factory size.
- 2
Enter new tire
The size you want to put on.
- 3
See comparison
Diameter, speedometer error, ground clearance change.
Frequently Asked Questions
Plus-sizing rules
New tire diameter should be within 3% of OEM. Over that causes speedometer error, gearing issues, rubbing.
Reading tire size
225/65R17: 225mm width, sidewall is 65% of width (146mm), R=radial, 17-inch wheel. Diameter = 2×146 + 17×25.4 = 724mm / 28.5in.
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100% Privacy. This tool runs entirely in your browser. Your data is never uploaded to any server.