How to Check Tire Size: Reading the Numbers on Your Sidewall

Your tire size is printed right on the tire itself — but the string of numbers and letters looks like a code until you know what each part means. Once you do, you can read it off any tire in about 30 seconds.

Where to Find Your Tire Size

There are three places to look:

• The tire sidewall — the outer edge of the tire, facing you when the vehicle is parked
• The driver's door jamb sticker — a white or yellow label inside the driver's door frame that lists the factory-recommended tire size
• The owner's manual — usually in the maintenance or specifications section

The sidewall is the most direct source. The door jamb sticker tells you what size your vehicle was originally designed to use, which may or may not match what's currently on the car if tires were ever swapped.

How to Read the Tire Size Code

A standard passenger tire size looks like this:

P215/65R16 98H

Each section tells you something specific.

So P215/65R16 means: passenger tire, 215mm wide, sidewall height is 65% of 215mm, radial construction, fits a 16-inch rim.

The Two Numbers That Matter Most for Replacement

When buying replacement tires, the three numbers you'll hear most are width/aspect ratio/wheel diameter — in the example above, that's 215/65/16. These determine whether a tire physically fits your wheel and clears your wheel well without rubbing.

🔢 A wider tire (higher first number) gives more contact patch. A lower aspect ratio (second number) means a shorter sidewall. These changes affect handling, ride comfort, fuel economy, and speedometer accuracy — even if the tire technically fits the rim.

What the Load Index and Speed Rating Tell You

Load index is a number that corresponds to a maximum weight rating. A load index of 98 means each tire can support roughly 1,653 pounds. You don't need to memorize the chart, but you do need to make sure a replacement tire's load index meets or exceeds the original spec — especially on trucks and SUVs that carry cargo or tow.

Speed rating is a letter tied to a maximum speed. Common ratings include:

• S — up to 112 mph
• T — up to 118 mph
• H — up to 130 mph
• V — up to 149 mph
• W / Y — 168 mph and above

For most everyday drivers, speed rating affects tire construction stiffness and heat resistance more than it limits actual driving. Replacing a higher-rated tire with a lower-rated one can matter in ways beyond top speed.

When the Sidewall Shows Something Different

Not every tire follows the standard passenger format. You might see:

• LT265/70R17 121/118S — a light truck tire with a dual load rating (single and dual rear wheel configurations)
• 275/40ZR20 — a performance tire with the speed rating embedded in the size
• T125/70D16 — a compact spare ("T" for temporary, "D" for diagonal/bias-ply construction)
• ST205/75R15 — a special trailer tire, not meant for passenger use

The prefix letters and additional markings shift based on tire category and intended use. Reading the full string — not just the three core numbers — helps you understand what you're actually looking at.

Cross-Checking the Sidewall Against the Door Sticker

🚗 Your door jamb sticker lists the tire size the vehicle manufacturer specified for that exact trim and configuration. If the tire on your car matches the sticker, you know it's the factory size. If the numbers differ, someone installed a non-stock size at some point — which isn't always wrong, but it's worth knowing.

The sticker also lists the correct inflation pressure. That's separate from anything printed on the tire itself. The max pressure molded into the tire sidewall is not your target inflation — it's the tire's structural ceiling.

Why the Same Vehicle Can Have Different Sizes

Even identical model years from the same automaker can come with different tire sizes depending on:

• Trim level — higher trims often have larger wheels and lower-profile tires
• Optional wheel packages — dealer or factory upgrades that swap rim diameter
• Regional specifications — some markets use different configurations
• Previous owner changes — aftermarket wheels, lifted suspensions, or plus-sizing

This is why checking the actual tire and the actual door sticker on your specific vehicle matters more than looking up a size online for your make and model. Two cars can share a year, make, and model but wear meaningfully different tires.

The numbers are all there on the sidewall — once you know the format, your tire tells you exactly what it is. Whether those specs match your vehicle's requirements, your driving conditions, and your load needs is a different question — one that depends on the specifics of your own situation.