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How to Read Tire Sizes and Know What They Mean — Are Bigger Tires Better?

By Tire Agent Staff

January 25, 2022


Source: Goodyear

Numbers taken out of context could be gibberish to you. For example, if you read "Ohtani grounded into a four, six, three double play," you might think the author has gone insane.

But if you're a baseball fan, you understand that Ohtani hit a ground ball to the second baseman who threw it to the shortstop for the first out, who then finished the play by throwing to first base and recording the second out for a double play. Pretty standard baseball lingo.

No, we're not here to teach you how to keep score of a baseball game. While it might not be as exciting as a bang-bang play at the plate, understanding tire lingo is much more important.

We're going to show you how to accurately interpret the numbers seen on tires and help you find the correct size for your vehicle. I'll write it in my best Vin Scully voice to make it more entertaining for you.

How to Find the Right Tire Size for Your Vehicle

There are a couple of easy methods to find the manufacturer's recommended tire size for your vehicle.

  • Check your owner's manual. You know that handy guide that comes with all cars that's probably collecting dust inside your glove box? If you can't find the manual, try the second method. Many manufacturers publish their owners' manuals online. Look there if it's gone from the glove box.
  • Check the door jamb. The second method for finding your manufacturer's tire size recommendation is by looking at the place card inside your vehicle. You'll find this attached inside the driver's side door jamb, in most cases.


Sample tire placard from Bridgestone/Firestone

Actual tire placard by Honda from NHTSA

Now that you know the correct tire size for your vehicle, we suggest sticking with the recommendations. If you try to use a different tire size, it could lead to performance and safety issues.

If you have your heart set on changing sizes, maybe because you're looking to add custom rims, your best bet is to speak with a tire professional to find a size range that works for your vehicle.

Don't understand all the numbers on your tires? Keep reading for a quick breakdown of what the numbers indicate.

Correctly Reading Tire Size on the Sidewall of Your Tires

3 ways tires are measured

Have you ever looked at the writing on your tires? There are tons of information on them that you might not understand. In this post, we focus solely on tire size. We have a related post that explains more about cracking tire codes.

There are three key pieces of information that you need to know. Once you understand these numbers, you can look at the tires on your car to see the size you're currently using and make sure they meet recommendations.

One of the most common tire sizes is P 215/65 R 15. The P stands for passenger vehicle tire. You might see LT or ST instead of the P. Those stand for light truck tire and special tire.

But we're going to focus on the numbers and what they mean. Let's take a look at them now.


Source: NHTSA

1. Tire width

In the P 205/65 R 15 example, the 205 means the tire is 205 millimeters wide, looking at the tire head-on.


2. Aspect ratio

The second number, 65, represents the tire's aspect ratio. Aspect ratio indicates the tire's height is 65% of the tire's width. The bigger the aspect ratio, the larger the sidewall of the tire.

You can check out our extensive report on tire aspect ratio here.


3. Wheel or rim diameter

The final number of importance is 15. The 15 signifies the rim diameter of the wheel that the tire will fit. So, the rim size that you'd need is 15-inches.

Do these numbers on your vehicle's tires match the manufacturer's recommendations? If not, speak with a tire professional to ensure you're driving safely. To shop for tires by size from Tire Agent, from any page, select the "SHOP BY SIZE" option, then enter your width, aspect and diameter.


More resources to find the perfect tire

Tire size is just one factor when looking for the perfect match. There are other things to consider. Don't worry. We've got you covered.

Guide to tire temperature ratings

In this guide, we explain one set of characters on your sidewalls: tire temperature grades.

Understanding tire treadwear ratings

Treadwear ratings are supposed to help us determine the value of a tire and answer questions like, how long will a tire last? And, is the tire’s expected life worth its price? Find tire tread wear info that you're looking for.

The meaning of tire traction rating

Tire traction scores refer to a tire’s ability to stop on wet pavement. The higher the rating, the shorter the stopping distance. Check out our complete breakdown here.