What do the 3 main numbers on a tire mean?

The three main numbers (for example, 225/65/17) stand for the tire's width in millimeters, the aspect ratio (the sidewall's height as a percentage of the width), and the wheel rim diameter in inches.

What does the R mean on a tire?

The "R" stands for Radial construction. It means the internal fabric cord plies run radially across the tire (at 90 degrees to the direction of travel). Almost all modern consumer tires are radial.

What is the 91H or 102T at the end of the tire size?

That is the Service Description. The number is the Load Index (how much weight the tire can carry), and the letter is the Speed Rating (the maximum safe sustained speed for that tire).

Is my tire width in mm or inches?

In the modern metric sizing system, the first number is always the width in millimeters. However, large off-road and mud-terrain tires sometimes use the imperial "flotation" system, where the first number (e.g., 35x12.50) is the overall height in inches.

Where can I find my tire code?

The full tire code is molded directly onto the outer sidewall of the tire in large print. You can also find the factory recommended code on the sticker inside your driver's side door jamb.

Full Tire Sidewall Decoder

Enter your full tire code sequence to instantly translate the numbers and letters into plain English dimensions and ratings.

Quick Answer

Decoding the standard tire sequence "P225/65R17 102H" reveals its exact specs: It is a Passenger vehicle tire, 225mm wide, with a sidewall height that is 65% of the width. It has Radial construction, fits a 17-inch rim, can safely support 1,874 lbs per tire (Load Index 102), and is rated for sustained speeds up to 130 mph (Speed Rating H).

Enter tire sidewall code

Anatomy of a Standard Tire Code (P225/65R17 102H)

Code Element	Position	What It Represents	Example Meaning
Service Type	P	Intended vehicle type	Passenger Vehicle
Section Width	225	Tire width from sidewall to sidewall	225 millimeters
Aspect Ratio	65	Sidewall height vs width	Height is 65% of 225mm
Construction	R	Internal ply design	Radial Plies
Rim Diameter	17	Required wheel size	17 inches
Service Desc.	102H	Combined Load and Speed	1,874 lbs max / 130 mph max

Parsing Formula

Code = [Prefix][Width]/[Aspect Ratio][Construction][Rim Diameter] [Load Index][Speed Rating]

Prefix = P, LT, ST, or blank (no prefix = Euro metric)
Width = 3 digits in millimeters
Aspect = 2 digit percentage of width
Construction = R (Radial), D (Diagonal), or B (Belted)
Example: "265/70R17" parsed means Width=265mm, Aspect=70%, Construction=Radial, Rim=17"

Frequently Asked Questions

Related Tire Rating Calculators

UTQG Tire Rating Decoder Tire Treadwear Rating Comparison Tire Age from DOT Code Calculator DOT Year Code Reference Chart

Back to All Tire Rating Calculators All Calculators