Tire Size Calculator
Decode tire sizes and compare alternatives — understand what 225/65R17 actually means.
Decode a Tire Size
Or enter a full size code like 225/65R17:
Tire Dimensions
Total Diameter (in)
Sidewall Height (mm)
Circumference (in)
Revs per Mile
Compare Two Tire Sizes
How to Read a Tire Code
225 — Width
Section width in millimeters from sidewall to sidewall.
65 — Aspect Ratio
Sidewall height as % of width. 65% of 225mm = 146mm sidewall.
R17 — Rim Diameter
Wheel diameter in inches that the tire fits on.
Frequently Asked Questions
What happens if I use a different tire size?▼
Changing tire diameter affects speedometer accuracy (because the odometer measures wheel rotations, not actual distance), gearing, and potentially clearance. A tire 3% larger in diameter makes your speedometer read 3% low — you'll actually be going faster than it shows. Width changes affect handling and can cause rubbing on fenders. The comparison tool above shows the exact speedometer difference.
What is aspect ratio in tire sizes?▼
The aspect ratio (the middle number, e.g., '65' in 225/65R17) is the sidewall height expressed as a percentage of the tire's width. A 225/65R17 has a sidewall of 225 × 0.65 = 146.25mm. Lower aspect ratios (40–50) mean a sportier, lower-profile look with stiffer handling. Higher ratios (65–80) give a taller sidewall with a more comfortable ride.