Date Posted: Jul 27, 2026
How to Read Tire Size
Take a peek at the sidewall of any tire, and you’ll eventually spot a string of letters and numbers that probably looks more like a secret code than it does essential information.
Something like “225/65R17 102H” isn’t exactly self-explanatory to most people. But understanding these tire markings is a lot easier than you think it’s going to be at first glance. It’s all about knowing what each part represents.
Here’s what you need to know about how to read a tire size, including where to look for the markings and why getting your tire size correct is so important in the first place.
Where to Find Your Tire Size
Wondering how to tell tire size when it comes to your current ride? Look carefully at the sidewall. The full size designation is molded right into the rubber, and it’s easy to spot once you know what you’re looking for.
That’s not the only place you can find your recommended tire size in a pinch, though. Try checking out these other spots:
- Inside your driver’s side door jamb
- On the tire information placard attached to your vehicle
- In your owner’s manual
Breaking Down a Tire Size
Here’s a really common example to help you get the hang of breaking down an individual tire size number meaning – 225/65R17 102H. Each part tells you something different about that tire.
Tire width
The first number represents the tire width, which is 225 millimeters in our example. Generally speaking, wider tires offer drivers more grip, while narrower alternatives can improve fuel efficiency. Narrow tires often work better under certain winter conditions, as well.
Aspect ratio
The second number covers the tire’s aspect ratio, the height of the tire’s sidewall as a percentage of its total width. In our example tire, this number is 65, which indicates the sidewall height is 65 percent of the tire’s width.
Lower aspect ratios usually correlate to shorter sidewalls and sportier handling. But a higher aspect ratio means more cushioning, helping to facilitate smoother rides over rough roads.
Tire construction
The next detail refers to tire construction. In our example, R stands for radial construction, which is what’s used on the vast majority of light trucks and passenger vehicles. Unless you have a vintage vehicle or specialty ride, you’ll rarely see anything else.
Wheel diameter
The next number indicates the diameter of the wheel the tire was designed to fit, so our example tire was made to fit a 17-inch wheel. A tire needs to match the wheel diameter exactly, so you won’t be able to safely fit an 18-inch tire onto a 17-inch wheel, and vice versa.
Load index
Load index follows wheel size – 102 in our example – representing the amount of weight each tire is designed to carry once properly inflated. The higher the number, the higher the carrying capacity. It’s generally enough to know your vehicle manufacturer’s recommended load rating and make sure any replacement tires you buy either meet or exceed that.
Speed rating
Last but not least, we have the speed rating – H. This correlates to the maximum speed the tire was made to handle under the right conditions. Always default to manufacturer recommendations for safe, optimal performance.
Once you understand what each section represents, understanding overall tire size meaning is pretty simple. However, changing even part of this equation will affect how your vehicle handles, brakes, rides, and performs.
How to Read Truck Tire Size
You can apply the same basic method when assessing truck tire size meaning. However, truck tire sizes sometimes include additional information.
For example, let’s say a truck tire marking reads LT265/70R17. The “LT” at the beginning of the marking stands for “light truck,” meaning the tire in question was designed for SUVs, trucks, and similar vehicles that regularly carry heavy loads.
Occasionally, truck tires will also include a ply rating or load range, such as “Load Range E.” This tells you how much weight that tire was designed to support.
Why It’s Essential to Use the Correct Tire Size
Choosing the right tire size for your vehicle is about more than simply making sure it fits your wheel. Getting things right also helps you maintain factors like safe handling, accurate speedometer ratings, fuel efficiency, ride comfort, and proper braking performance.
A tire size that’s off can even affect steering feel, as well as electronic safety systems like ABS and traction control. For that reason, it’s important to speak with a qualified tire professional before changing up your tires for appearance or performance reasons.