How to read tire codes: What those letters and numbers really mean

Before you can start decoding, you’ll need to locate the code on your tire. It’s usually on the sidewall—the smooth area between the tread and the wheel rim. In the U.S., tire codes include a mix of letters and numbers, often separated by a slash.

We’ll use this sample tire size code to help explain what each number and letter means:
P195/75R16 94S

Most tire codes in the U.S. start with a letter or letters that show what type of tire it is. For example, P stands for passenger vehicle tire. Other common letters include LT, which stands for light truck tire, and ST for special trailer tire.

The three digits that follow indicate the tire's width in millimeters across the tread. For example, 195 means the tire is 195 millimeters wide. If you want the tire’s size while shopping for a replacement, this is one of the key numbers to understand.

The next two numbers are the tire’s aspect ratio—how tall the sidewall is compared to the width of the tire. It’s shown as a percentage. An aspect ratio of 75 means the sidewall height is 75% of the tire’s width.

• Lower ratio (shorter sidewall): Less flex in the tire, which can improve steering response—but it also means you’ll feel more of the road.

• Higher ratio (taller sidewall): More flex, which helps absorb bumps and rough roads—but handling may feel less sharp.

Next comes a single letter that tells you how the tire is built. The most common letter is R, which stands for radial—a construction type where the internal layers run straight across from one side of the tire to the other. This design helps the tire stay flexible and stable. Other types include D for diagonal and B for belted. Radial tires are the most common choice for passenger vehicles today.

The two-digit number that follows is the tire's wheel diameter in inches. For example, 16 means the diameter is 16 inches. This measurement is another important part of understanding tire size when shopping for a new one.

Load index is shown as a two- or three-digit number that tells you the maximum weight a tire can safely carry. For example, a tire with a load index of 94 can support 1,477 lbs. To interpret this number, check a load index conversion chart.

This number applies to one tire. Multiply it by the number of tires on your vehicle to get the total load capacity. So, in this example, a full set of four tires can support up to 5,908 lbs.

Overloading your tires can lead to heat buildup and other issues. If your car looks like it’s hauling bricks or bottoms out every time you leave the driveway, your tires are probably carrying more than they should.

The final letter on a tire code is the tire speed rating—the maximum speed you can drive on those tires for an extended period. A tire with a speed rating of S, for example, supports speeds of up to 112 mph.

While most drivers don’t regularly reach these limits, choosing a tire with the correct speed rating may help with your vehicle’s handling, braking, and stability. In some cases, vehicle inspections, warranties, or insurance policies may look at the manufacturer’s original tire specifications, so choosing a tire with an equal or higher rating could help avoid potential complications.

Exceeding the rated speed occasionally might not cause immediate issues, but consistently driving faster than a tire’s limit can lead to performance problems—or even failure over time. That said, even if your tires are rated for higher speeds, always follow posted speed limits.

Here are some common speed ratings. These can vary slightly, so it’s always a good idea to check with the tire manufacturer for specifics.

• L = 75 mph

• M = 81 mph

• N = 87 mph

• P = 93 mph

• Q = 99 mph

• R = 106 mph

• S = 112 mph

• T = 118 mph

• U = 124 mph

• H = 130 mph

• V = 149 mph

Tire codes offer a lot of helpful information—but they don’t tell you everything. You’ll also find other markings on the sidewall that give you even more insight, including:

• DOT code: Shows manufacturer details and the tire’s production date.

• Maximum inflation pressure: The highest pressure the tire can safely hold—not the same as the recommended tire pressure.

• Treadwear grade: Indicates how long a tire is expected to last. A higher number generally means longer tread life.

• Traction grade: Rated AA, A, B, or C—AA provides the best traction.

• Temperature grade: Rated A, B, or C—A offers the highest resistance to heat.

Tire condition affects how well your vehicle stops, handles, and maintains traction—which all play a role in driving safely. If worn or damaged tires contribute to an accident, they may be part of the conversation during a claim review. That’s why it’s important to understand the codes on your tires that can help you keep your tires in good shape.

Whether your tires are new, worn, or somewhere in between, Dairyland^®, a brand of the Sentry Insurance Group, offers flexible auto insurance options that work with a wide range of budgets. Have questions? Give us a call at 800-334-0090.