How to Read a Tire: Understanding Tire Sizes, Ratings and Sidewall Markings

If you've ever looked at the sidewall of a tire and wondered what all the numbers and letters mean, you're not alone.

A tire sidewall contains important information about the tire's size, construction, load capacity, speed rating, and manufacturing date. Understanding these markings can make it much easier to find the right replacement tires for your vehicle.

One of the most common examples looks something like this:

225/65R17 102H

At first, it may look like a random combination of numbers and letters. Once you know what each part means, it's actually pretty simple to read.

Understanding Tire Size

Let's break down 225/65R17.

225: Tire Width

The first three numbers represent the tire's width in millimeters.

In this example, 225 means the tire is approximately 225 millimeters wide from sidewall to sidewall.

65: Aspect Ratio

The second number represents the tire's aspect ratio.

An aspect ratio of 65 means the height of the tire's sidewall is approximately 65% of the tire's width.

A lower aspect ratio generally means a shorter sidewall, while a higher aspect ratio generally means a taller sidewall.

R: Tire Construction

The letter R stands for radial construction.

Radial tires are the standard construction used on most modern passenger cars, trucks, SUVs, and crossovers.

You may also see other markings depending on the type of tire and its intended application.

17: Wheel Diameter

The final number in the size is the wheel diameter, measured in inches.

In 225/65R17, the tire is designed to fit a 17 inch wheel.

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Understanding Load Index and Speed Rating

After the tire size, you will usually find a number followed by a letter.

In our example:

102H

These markings tell you about the tire's load capacity and speed rating.

102: Load Index

The load index is a numerical code that corresponds to the maximum weight the tire is designed to carry under specified conditions.

The number itself isn't the weight in pounds. It must be matched to a load index chart.

When replacing tires, the load rating should be appropriate for the vehicle.

H: Speed Rating

The final letter represents the tire's speed rating.

Different letters correspond to different maximum rated speeds under specified testing conditions.

Common passenger tire speed ratings include:

T, H, V, W and Y

It's important to select a tire with a speed rating appropriate for the vehicle and its intended use.

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What Does the DOT Number Mean?

You may also notice a longer code beginning with DOT on the tire sidewall.

The Tire Identification Number, or TIN, provides information used to identify the tire and its production.

The last four digits are particularly useful to consumers.

For example:

3625

The first two digits indicate the week the tire was manufactured, while the last two indicate the year.

In this example, the tire was manufactured during the 36th week of 2025.

When buying tires, checking the manufacturing date can help you understand when the tire was produced.

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Other Tire Markings You May See

Depending on the tire, you may find additional letters and symbols on the sidewall.

P

P generally identifies a tire designed for passenger vehicles.

LT

LT indicates a light truck tire.

ST

ST is commonly used for special trailer tires.

XL

XL generally indicates an extra load tire designed to carry a higher load than a standard version of the same size under specified conditions.

M+S

M+S means Mud and Snow. This marking is commonly found on tires designed for use in a variety of conditions.

3PMSF

The three peak mountain snowflake symbol indicates that a tire meets specific performance requirements for severe snow conditions.

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Why Tire Markings Matter

Understanding tire markings isn't just useful when you're shopping online.

Using the correct tire size and specifications is important for the vehicle's performance and safe operation.

Before purchasing a replacement tire, make sure you verify:

• Tire size
• Load index
• Speed rating
• Tire type
• Wheel diameter
• Intended application
• Manufacturing date

Your vehicle owner's manual and the tire information placard on the vehicle can also provide important information about the correct tire specifications.

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How to Find the Right Tire

The easiest place to start is by looking at the tires currently installed on your vehicle.

Find the tire size printed on the sidewall and use it as a starting point when shopping for replacements.

For example, if your current tire says:

225/65R17 102H

you can use that information to find tires available in the same size and with appropriate specifications.

From there, you can compare different brands, tread designs, performance characteristics, warranties, and prices.

This is especially useful when comparing premium, mid-range, budget, and ultra-budget tires.

You don't always have to buy the same brand that came on your vehicle.

The important thing is finding a tire that is properly matched to the vehicle and your driving needs.

The Bottom Line

The numbers and letters on a tire aren't as complicated as they first appear.

Once you understand the basic markings, you can quickly determine the tire's:

Width, aspect ratio, construction, wheel size, load rating, speed rating, and manufacturing date.

Knowing how to read your tire gives you more information when comparing replacement options and helps you make a more informed purchasing decision.

Whether you're looking for a premium tire, a budget option, or an ultra-budget alternative, knowing what's written on the sidewall is the first step toward finding the right tire.

At TireOrigin, we're here to help make the tire-buying process easier by giving dealers and consumers the information they need to make smarter tire decisions.