How To Tell What Size My Tires Are | Read The Numbers Right

Check the tire sidewall first, then match that code to the driver-door placard and owner’s manual before buying a replacement.

If you need your tire size, start with three spots: the sidewall, the sticker on the driver-side door jamb, and the owner’s manual. The sidewall shows what is mounted on the car now. The door placard shows what the car maker wants on that vehicle. That placard is the one to trust when it’s time to replace tires.

A lot of drivers read one line of numbers, shrug, and hope the tire shop sorts it out. You don’t have to do that. Once you know what each part means, you can tell whether your car is wearing the right size, whether the front and rear match, and whether a replacement listing is pointing you to the right tire.

Start With The Three Places That Matter

The easiest read is on the sidewall. You’ll see a code such as 215/60R16 95H. That code gives you the width, aspect ratio, construction type, wheel diameter, load index, and speed rating. It’s the mounted tire’s full ID card.

Next, open the driver-side door and find the Tire and Loading Information sticker. On most cars, that label lists the factory tire size, cold tire pressure, and load details. The pressure and size on that vehicle label are the numbers set for that car, not just the tire.

Then check the owner’s manual. This helps when the placard is worn, missing, or hard to read. It can also clear up cases where one trim level uses a different wheel size than another.

• Use the sidewall to see what is on the car right now.
• Use the door placard to see what size the vehicle was built to use.
• Use the manual when the first two sources don’t agree or one is missing.

Telling What Size Your Tires Are From The Sidewall

Read the code from left to right. Each piece answers one plain question. How wide is the tire? How tall is the sidewall? What wheel does it fit? How much weight can it carry? How fast is it rated to run?

Say your tire reads P215/60R16 95H. Here’s the plain-English version:

• P = passenger tire
• 215 = tire width in millimeters
• 60 = sidewall height as a percent of the width
• R = radial construction
• 16 = wheel diameter in inches
• 95 = load index
• H = speed rating

That means the tire is 215 mm wide, the sidewall height is 60% of that width, and it fits a 16-inch wheel. The last two marks matter too. Two tires can share the same size and still differ in load index or speed rating, which is why copying only the first numbers can trip you up.

Extra letters can show up at the front or end of the code. LT means light-truck tire. ST means trailer tire. T often marks a temporary spare. M+S or the three-peak mountain snowflake symbol points to winter traction classes, not the base size.

If you want a second read on sidewall markings, Michelin’s tire markings explainer lays out the same code families used on passenger tires, including size, load, and speed markings.

What Changes And What Stays The Same

Three parts of the code do most of the buying work: width, aspect ratio, and wheel diameter. If any one of those changes, you are no longer buying the same size. Load index and speed rating also need to stay at the vehicle’s stated level or higher, unless the car maker lists another fitment for that model.

Mark On The Tire	Sample	What It Tells You
Tire type	P / LT / ST / T	Shows whether the tire is for passenger cars, light trucks, trailers, or a temporary spare.
Width	215	The tire’s section width in millimeters, measured at its widest point.
Aspect ratio	60	The sidewall height as a percent of the width.
Construction	R	Radial construction, which is what most passenger vehicles use.
Wheel diameter	16	The wheel size in inches that the tire fits.
Load index	95	A coded load capacity number that must meet the vehicle’s requirement.
Speed rating	H	The tire’s rated top-speed class under test conditions.
Service marks	M+S / 3PMSF	Shows mud-and-snow or severe-snow service class, not a different size.
DOT code	DOT … 2324	Shows maker, plant, and manufacture week/year; the last four digits are the date code.

Why The Door Placard Beats The Sidewall For Replacement Tires

The tire on the car may not be the tire the car was built to use. A past owner may have changed wheel size, fitted a cheaper tire, or mixed brands and sizes after a blowout. The NHTSA tire safety page points drivers to the door placard for this reason. It lists the size and pressure the vehicle was set up for at the factory.

This also clears up one of the biggest mix-ups drivers make. The maximum pressure printed on the tire sidewall is not your everyday target pressure. Use the placard or manual for the vehicle’s cold pressure setting.

When Front And Rear Tires Don’t Match

Some cars use one size in front and another in back. Sports cars and some performance trims do this on purpose. Read both axles on the placard, or read each tire on the car before you order. Don’t assume all four match just because the wheels look the same from ten feet away.

When The Spare Throws You Off

A compact spare often carries a different size code, narrower tread, and lower speed limit. That’s normal. Don’t buy full-time replacement tires by copying the spare unless you are replacing the spare itself.

Common Mistakes That Lead To The Wrong Tire Size

Most ordering mistakes come from reading only part of the sidewall code. A driver sees 16 inches and stops there, or copies the width and misses the aspect ratio. One skipped number is all it takes to order a tire that won’t fit the wheel, rubs the fender, or changes the way the speedometer reads.

Mix-Up	What Goes Wrong	What To Do Instead
Reading only the wheel size	You order any 16-inch tire, even if width and sidewall are wrong.	Copy the whole code, not just the last number.
Using the spare as the reference	You end up shopping a temporary-use tire size.	Read a regular road tire or the placard.
Ignoring front/rear differences	You order four matching tires for a staggered setup.	Check each axle before you buy.
Skipping load index	The tire may fit the wheel but miss the vehicle’s load need.	Match the listed load index or go higher if approved for the vehicle.
Skipping speed rating	You buy the right size with the wrong performance class.	Match the placard, manual, or approved replacement spec.
Trusting what is already mounted	You repeat an old mismatch from a past owner.	Use the placard as the tie-breaker.

A Short Check Before You Order

Before you buy, take two photos: one of the full sidewall code and one of the driver-door placard. That gives you a clean record you can read later without crouching in a parking lot. If the car has different sizes front and rear, take one photo from each axle.

1. Read the full sidewall code, not just the wheel diameter.
2. Match that code against the door placard.
3. Check whether front and rear sizes differ.
4. Match load index and speed rating.
5. Ignore the spare unless you are shopping for the spare.
6. Use the owner’s manual if the placard is missing or damaged.

If the sidewall and placard disagree, use the placard first. If the car has aftermarket wheels or suspension changes, then the current size may be deliberate. In that case, read the wheel size, tire clearance, and fitment notes before you buy another set.

Use The Placard As The Tiebreaker

You can tell your tire size in under a minute once you know where to read it. The sidewall gives the mounted tire’s code. The door sticker gives the factory size and pressure. The manual backs it up. Put those three together and you’ll know whether the tire on the car is the right size, whether a listing matches, and whether you’re about to order the wrong thing.