🇺🇸 Free tire age & DOT code tools for US drivers
Based on NHTSA 49 CFR § 574.5Vehicle-label-first pressure guidance
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TIREDOTCODEUSA 🇺🇸
Tire age & DOT date code decoder
Tire sidewall numbers

How to Read Tire Size

A marking such as 225/60R17 describes nominal tire geometry and construction. Additional symbols, such as 99H, describe load index and speed capability. These markings do not by themselves confirm that a tire is approved for a specific vehicle.

225/60R17

225 mm width · 60% aspect ratio · radial · 17-inch wheel

225 — Section width

Nominal width in millimeters from sidewall to sidewall under standardized measuring conditions.

60 — Aspect ratio

Sidewall height is nominally 60% of 225 mm—not 60 mm.

R — Construction

R identifies radial construction. It is not a radius measurement.

17 — Rim diameter

The tire is designed for a wheel with a 17-inch bead-seat diameter.

What does 99H after the size mean?

In a marking such as 225/60R17 99H, 99 is the load index and H is the speed symbol. Their meanings come from standardized tables. Replacement tires should meet the vehicle manufacturer’s requirements; a higher-looking number does not independently confirm fitment.

Tire size vs wheel size vs vehicle fitment

  • Tire size: width, aspect ratio, construction, and rim diameter.
  • Wheel size: diameter, width, offset, bolt pattern, and load capacity.
  • Vehicle fitment: adds clearance, axle load, service description, approved pressure, and system compatibility.

Nominal dimensions vary slightly by tire model and measuring rim. Confirm published specifications for the exact product.

Compare two tire sizesDiameter and speedometer estimate →Decode more sidewall markingsLoad, speed, DOT and UTQG glossary →

Frequently asked questions

What does 225/60R17 mean?

225 is nominal section width in millimeters, 60 is sidewall height as a percentage of width, R means radial construction, and 17 is the matching wheel diameter in inches.

Is tire size the same as wheel size?

No. The final number identifies wheel diameter, while the complete tire size also includes section width, aspect ratio, and construction.

Can I use a different tire size?

A dimension calculator can compare geometry, but fitment also requires manufacturer-approved load capacity, wheel width, clearance, and vehicle-system compatibility.