Date Posted: Jul 27, 2026
How To Read Tire Size | Wentworth Tire
Looking at the sidewall of your tire can feel a bit like trying to read a foreign language. The surface is stamped with a string of what looks like random numbers and letters. However, learning how to tell tire size is one of the easiest automotive skills you can pick up. The letters and numbers are actually a precise blueprint that shows exactly how wide your tire is. It also tells you how much weight it can carry and how fast it can safely travel.
Equipping your vehicle with the correct tire size has a direct impact on traction and braking, and even your gas mileage. Let's break down this automotive code so you can easily find your next set of tires.
Where to Find Your Tire Size
The most obvious place to look is right on the tire's sidewall, but that might not be the best place to start. If you bought the vehicle used, what if a previous owner installed the wrong tire size? To find the exact size recommended by the vehicle's manufacturer, look for the tire information placard. You'll usually find this printed on a sticker inside the driver's side door jamb. If it's not there, check the inside of your glove box door and the gas tank hatch. If all those methods fail, flip open your vehicle's owner's manual.
Standard Tire Size Meaning
Most passenger vehicles on the road today use a metric or "P-metric" sizing system. Let's look at a very common example size: P215/65R15. Now let's figure out the exact tire size meaning from left to right.
The Tire Type (P): The very first letter designates the vehicle class the tire was engineered for. "P" stands for P-metric. This means it's designed for passenger vehicles like sedans, minivans, crossovers, and light SUVs. If a tire doesn't have a letter at the beginning, that means it's a Euro-metric tire. Euro-metric tires are very similar, but they may have subtle variations in load capacity.
Tire Width (215): The three-digit number following the initial letter indicates the width of the tire in millimeters. This is measured in a straight line from the outermost edge of one sidewall to the outermost edge of the opposite sidewall. In our example, the tire is 215 millimeters wide.
Aspect Ratio (65): Located immediately after the forward slash (/), this two-digit number represents the aspect ratio. This is a percentage that tells you the height of the sidewall relative to the tire's width. Here, the tire's sidewall height is exactly 65 percent of its 215mm width. A lower aspect ratio, like 45, means a shorter, high-performance sidewall. A higher number, like 75, means a taller sidewall and a shorter ride.
Core Structure and Rim Fitment
Continuing through the string of text, you'll find that the tire size number meaning shifts from metric dimensions to construction types and standard inches.
Internal Construction (R): The "R" stands for radial. Radial construction means the tire's internal cords run perpendicular to the travel direction. This is the industry standard for almost every passenger vehicle due to its superior grip and fuel efficiency.
Wheel Diameter (15): The final two-digit number in the main sequence tells you the size of the wheel rim in inches. A tire marked with a 15 must be mounted onto a 15-inch wheel rim.
How to Read Truck Tire Size
If you drive a heavy-duty pickup, a commercial vehicle, or a large towing SUV, learning how to read truck tire size is slightly different. Heavy-duty vehicles require better reinforcement, which changes the labeling system in one of two ways:
LT Metric Sizing: You might see the letters "LT" at the beginning of the code, such as LT285/70R17. LT stands for Light Truck. These tires have thicker sidewalls, extra steel belts, and higher ply ratings. They can safely manage large payloads and trailering demands.
Flotation Sizing: This system is frequently used for off-road and oversized truck tires. It bypasses the metric system entirely and uses inches, such as 35x12.50R17. The first number, 35, is the total height of the tire in inches. The final number, 17, remains the wheel rim diameter.
Don't Ignore the Service Description
Directly following the wheel diameter, you'll find a separate code consisting of a number and a letter, like 95H. The number is the load index, which cross-references to a specific weight capacity chart. The final letter is the speed rating, which notes the maximum safe speed the tire can sustain over prolonged periods under ideal conditions.
Let the Experts at Wentworth Tire Help
Now that you know how to read a tire size, you can easily search for the perfect set of replacements. If you're ready to upgrade your ride or need a seasonal tire swap, our TIA-certified technicians at Wentworth Tire are here to guide you.