Home › Guides › How to Read Tire Size Numbers

How to Read Tire Size Numbers

Decode markings like 225/65R17. Understand width, aspect ratio, and speed ratings.

Every tire has a size code stamped on its sidewall. Here is exactly what each number means.

Example: 225/65R17 102H

• 225 — Tire width in millimeters (sidewall to sidewall)
• 65 — Aspect ratio: sidewall height is 65% of the width
• R — Radial construction (standard for all modern tires)
• 17 — Wheel diameter in inches
• 102 — Load index (102 = 1874 lbs per tire)
• H — Speed rating (H = up to 130 mph)

Why It Matters

Installing the wrong size affects speedometer accuracy, fuel economy, clearance, and handling. Always match your OEM size unless you have a specific reason to deviate.

Finding Your Size

Use the TireSize411 search tool to instantly look up the correct size for your exact vehicle. The size is also printed on the driver door jamb sticker.