Tire Size Calculator

Compare two tire sizes to see differences in diameter, circumference, and speedometer error.

How Tire Sizing Works

A tire size like 205/55R16 means:

• 205 — width in millimeters
• 55 — sidewall height as a percentage of width
• R — radial construction
• 16 — wheel diameter in inches

Plus Sizing Rules

• Keep overall diameter within 3% of original
• Reduce sidewall by 5% for each +1 inch rim
• Increase width by 10mm for each +1 inch rim