How to read the size of a tire?

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How To Read a Tire Size?

Tire size is hard to read, especially when you have never done that.

Asking an expert to help you get out of this trouble will cost you time and money, plus it is difficult for a self-sufficient person who doesn’t like to rely on the help of others.

But, you don’t need to worry about that because this article will guide you on how to read the size of a tire.  

How to read the size of a tire

After reading this guide, inspecting the tire size will never be difficult for you, and you will be able to do it in a few seconds.

So, stick with it, and we will see you through to the end until you get the best results.

How can I read the size of my tire?

If you have a tire, you might see a piece of information labeled on its sidewall in alphabetic and numeric characters.

This particular data is the tire size that tells you the comprehensive details about the tire. We will guide you on how to get detailed info on the tire using that specific information. We will take P225/70R16 as an example of tire size to guide how to read it.

Type of Tire:

The high chances are that the first letter you will probably see on a tire size is P. It indicates which type of tire you’re using.

The P means you have a P-metric tire, referring to tires made to specific standards within the United States, intended for passenger vehicles

If you see a tire size beginning with no letter, such as 225/70R16 91S, it is a Euro metric tire. Both P-metric and Euro-metric tires have different load capacities.

On the other hand, if you point at the letter LT, the beginning or the end of the tire size means that the tire is intended for light trucks.

These tires require high inflation pressure compared to passenger tires


The three-digit numbers you see after the first letter indicate the tire’s width in tire size. For instance, in a tire size P225/70R16 91S, the tire’s width is 225.

These three digits designate the tire’s width from sidewall to sidewall and are calculated in millimeters. 

Aspect Ratio:

The next comes of the tire size is the aspect ratio. It is defined as the ratio of the height of the tire cross-section to its width. The two-digit number that comes after the slash mark indicates the tire’s aspect ratio

For instance, in a tire size P225/70R16 91S, the aspect ratio is 70, meaning the tire’s height equals 70% of its width. The bigger the aspect ratio, the greater the tire’s sidewall.


The alphabetic letter comes after the aspect ratio tells you the tire’s construction. If the letter is labeled as R, your tire is radial which means layers move radially across the tire. Most contemporary tires are radial tires. 

Wheel or Rim Diameter:

The next part of the tire size describes its wheel diameter. The two-digit number after the letter R is the wheel diameter of the tire.

For example, a tire with the P225/70R16 91S size would fit a wheel or rim with a 16-inch diameter.

Load Index:

The load index tells us how much your tire can lift load in pounds when it is properly inflated.

The following rim size in the list is the load index of the tire. Standard Load and Extra Load load indices are the two categories available for passenger tires. Extra load tires are those with a label on them that reads “XL”; otherwise, they are ordinary load tires.

The majority of tires are compatible with conventional loads, while extra-load tires are uncommon. This is because they’re only designed to work with heavy-weight vehicles.

Standard Load Euro-Metric: 225/70R16 91S

Extra Load Euro-Metric: 225/17R16 91S XL

Speed Rating:

The final point of view in the tire size hierarchy, denoted by the letter S in the alphabet, is the speed rating.

It displays the speed limit that your tire is capable of reaching. For instance, a tire with an S speed rating has a 112 mph top speed limit. Moreover, the speed rating will be 106, 130, and 140 mph for R, H, and V tires.

Read More: 7 Best Tires For Subaru Forester

What are the other Markings on tires?

Besides the tire size, it is also good to know the purpose of other tire markings.

They are as follows:

Dot Symbol:  

The tire’s sidewall bears the letter DOT, signifying compliance with the Federal Motor Vehicle Safety Standards.

Tire Identification Number:

The Tire ID Number is a series of 12 numbers and alphabets followed by the DOT symbol. You can find out when and where the tire was made there.

Air pressure number:

The number on the tire sidewall shows how much pressure your tire can handle.

Read More: Best Tires for Gravel Roads


It appears that all you need is an in-depth understanding of tires to read tire sizes. Every aspect of examining the tire size and other marking symbols has been covered in detail.

We hope that this article will expand your understanding of tire size and other important topics. If so, be sure to read some of our blog’s other intriguing topics.

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