Date Posted: Aug 28, 2026
How to Read Tire Size | FR Tire King
Take a look at the sidewall of almost any tire, and you’ll find a string of numbers and letters printed around the rubber. Something like 245/60R18 105H might look complicated — but it actually gives you a quick rundown of the tire’s size and capabilities. Once you know what each part represents, reading those markings becomes much simpler. That knowledge can come in handy when you’re comparing tires or preparing for a replacement.
A Tire Size Is More Than Just Numbers
Think of the tire marking as a short description of the tire. For example, 245/60R18 105H contains multiple pieces of information:
- 245: Tire’s width in millimeters
- 60: Tire aspect ratio
- R: Radial construction
- 18: Wheel diameter in inches
- 105: Load index
- H: Speed rating
The first section focuses mainly on physical dimensions. The last two markings tell you more about how much weight the tire can carry and the speed it’s designed to handle.
Start With the First Number on Your Tire
That’s the tire’s width from one sidewall to the other. So, a tire marked 245 is roughly 245 mm wide. The next number is the aspect ratio. In a 245/60 tire, the sidewall is 60% as tall as the tire is wide. Aspect ratio can make a difference in how a vehicle feels on the road. Tires with shorter sidewalls can contribute to more responsive handling — while taller sidewalls can provide additional cushioning over bumps.
That doesn’t mean you should choose an aspect ratio based solely on driving preferences. Your vehicle has specific tire dimensions for a reason, so use the manufacturer’s recommendations as your starting point.
Check the Letter and Wheel Number Next
The R stands for radial construction that’s used on the vast majority of modern passenger-vehicle tires. The number immediately after the R refers to the wheel diameter. In 245/60R18, the 18 means the tire is made to fit an 18-inch wheel. This is an easy detail to overlook when shopping for tires. The tire and wheel need to be compatible, so knowing your wheel diameter can help narrow down your replacement options.
What the Final Markings Tell You
After the basic size, you’ll find the load index and speed rating. These specifications describe important performance characteristics. The 105 in our example is the load index. That’s the largest load the tire can support when it’s inflated properly. The number itself isn’t the weight measurement, so it needs to be referenced against a load index chart. The H indicates the tire’s speed rating — the highest speed the tire can handle under certain conditions. When replacing your tires, make sure the load and speed ratings meet your vehicle manufacturer’s requirements.
Find Your Vehicle’s Recommended Size
If you’re trying to determine the right tire for your vehicle, don’t rely solely on the markings of the tires currently installed. There are a few places you can check for the manufacturer’s recommended specifications:
- Driver’s door or doorjamb: Look for the tire information placard that typically lists the recommended size and inflation pressure.
- Owner’s manual: This can provide tire specifications and other information specific to your vehicle.
- Current tire sidewall: The markings can help you identify what is currently installed, although they should be compared with the manufacturer’s recommendations.
- Tire professional: A qualified technician can help confirm the appropriate tire factors, such as size, load rating, and speed rating.
Your vehicle may have different recommended tire sizes depending on its trim level or wheel configuration. If you’re thinking about changing your tire or wheel size, professional guidance can help you understand how the change could affect your vehicle.
Other Markings You May Notice
The size designation isn’t the only information printed on a tire. You may also see markings that identify the tire brand, model, manufacturing info, or characteristics related to the tire’s intended use. Some tires have additional designations, such as winter performance or reinforced construction. These markings vary by tire, so their meaning depends on the specific product.
Turn to FR Tire King for Tire Advice
Understanding tire size meaning can make the replacement process easier — but you don’t have to decode everything by yourself. FR Tire King can help you determine what specifications your vehicle needs and answer questions about different tire options. Our expert team can also inspect your current tires and provide tire services when maintenance or replacement is needed. Whether you’re checking the markings on your existing tires or shopping for a new set, getting advice from a tire professional can help you make a more informed choice.
