What Tire Size Is My Car? | Read The Door Sticker

Your car’s tire size is usually listed on the driver’s door placard, in the owner’s manual, and on the tire sidewall.

If you need new tires, don’t start by guessing from the wheel size alone. A 17-inch wheel can wear several tire sizes, and two cars with the same rim diameter can need totally different widths, sidewall heights, load ratings, and speed ratings.

The fastest clean check is this: open the driver’s door and find the Tire and Loading Information placard. That label tells you the size your car was built to use, plus the cold tire pressure. If your car has different front and rear tires, that label usually shows both. If your current tires were changed by a past owner, the sidewall may show what’s on the car now, not what belongs there.

What Tire Size Is My Car? Start With The Placard

The placard beats guesswork because it ties the tire to your car’s weight, suspension, wheel fit, and factory clearances. That matters more than the numbers molded into a tire that may have been swapped later.

• Best source: the driver’s door placard or door jamb label.
• Next source: the owner’s manual.
• Third source: the current tire sidewall, but only if you know the tires are the right ones.

Read the placard closely. Some vehicles list one size for normal driving and another for a spare. Others show separate front and rear sizes. Trucks, vans, and some SUVs may list a different load range or tire type from what you’d see on a small sedan.

Which source should you trust most?

If the placard and sidewall disagree, trust the placard first. The only time to step away from it is when your car maker lists another approved size in the manual or on a second factory label. That does happen on trims with alternate wheel packages.

Also, don’t use the pressure number on the tire sidewall as your everyday inflation target. That sidewall figure is tied to the tire itself. Your car’s placard gives the pressure the vehicle maker wants for that vehicle.

How To Read The Numbers On Your Tire

Take a code like P225/65R17 102H. Each part says something different. Once you know how to split it up, finding the right replacement gets much easier.

Read The Size Code In Order

The first letters and numbers

P means passenger tire. LT means light truck. Then comes 225, which is the tire width in millimeters. The next number, 65, is the aspect ratio. That means the sidewall height is 65% of the tire’s width.

The middle and tail of the code

R means radial construction. 17 is the wheel diameter in inches. 102 is the load index, which tells you how much weight one tire can carry at the rated pressure. H is the speed rating. You may also see a DOT code elsewhere on the sidewall, but that is not the tire size.

NHTSA’s Tire and Loading Information Label advice points you to the door placard or owner’s manual for the right size, while Michelin’s tire-marking explanation breaks down what each letter and number on the sidewall means.

Marking	What It Means	Why It Matters
P	Passenger tire type	Matches the tire class your car was built around
LT	Light truck tire type	Seen on trucks and some heavy-duty SUV setups
225	Tire width in millimeters	Affects wheel fit and clearance
65	Aspect ratio	Changes sidewall height and ride feel
R	Radial construction	Common on modern road tires
17	Wheel diameter in inches	Must match the rim exactly
102	Load index	Needs to meet or beat the vehicle’s spec
H	Speed rating	Needs to meet or beat the factory rating
T	Temporary spare type	Used on compact spare tires only

That table gives you the reading order, but the door placard still decides what you should buy. A tire can match the rim diameter and still be wrong if the width, aspect ratio, load index, or speed rating is off.

When The Door Label And Tire Sidewall Don’t Match

This happens more often than people think. A car may be wearing snow tires, an aftermarket wheel package, a temporary spare, or a set chosen by a past owner who liked the look more than the fit.

• Aftermarket wheels: the tire may have been upsized to fit a larger rim.
• Seasonal setup: winter tires may use a smaller wheel and a taller sidewall.
• Staggered fitment: some cars use different sizes front and rear from the factory.
• Wrong replacement: a tire shop or owner may have fitted a near match that isn’t the approved size.

If your car uses staggered sizes, don’t assume all four tires are meant to match. Read both axles on the placard. If the label shows one front size and one rear size, keep that layout unless your car maker lists another approved setup.

Situation	What It Usually Means	What To Do
Placard and sidewall match	You’re likely on the stock size	Order the same size and match the load and speed ratings
Sidewall is larger than placard	Aftermarket wheel or upsized tire	Check the manual before buying another set
Front and rear are different	Staggered setup	Order by axle, not as a single four-tire size
Spare has a T prefix	Temporary spare	Do not match your full-size road tires to it
No placard or unreadable label	Label is missing or damaged	Use the owner’s manual or dealer VIN lookup

How To Buy Replacement Tires Without Guessing

Once you have the right size, you’re not done. Two tires with the same size code can still differ in load rating, speed rating, tread type, and season rating.

1. Write down the full placard size. Don’t stop at the rim diameter.
2. Check front and rear separately. Do this on every SUV, coupe, and trim with sporty wheels.
3. Match or exceed the load index. Don’t drop below factory spec.
4. Match or exceed the speed rating. This keeps the tire aligned with the car’s original rating.
5. Check the pressure on the placard. Set that after installation when the tires are cold.

If you want all-season, summer, or winter tires, that choice changes tread design, not the base size you should start from. Size first. Tire type second.

Common Mistakes That Cause Wrong Orders

A lot of bad tire purchases come from one shortcut: reading only the boldest number on the sidewall. A 17-inch tire is not one universal thing. A 225/65R17 and a 245/45R17 both fit 17-inch wheels, but they are nowhere near the same overall shape.

• Using only wheel diameter: this misses width and sidewall height.
• Copying the spare tire size: compact spares are not daily-driving tires.
• Ignoring load index: the tire may fit but still be under-rated for the car.
• Ignoring speed rating: this can change how the tire is rated for use.
• Trusting the current sidewall blindly: the tire on the car may not be the approved size.

There’s also the pressure mix-up. The pressure molded into the tire sidewall is not your normal fill target. Use the placard pressure for daily driving unless your car maker states a different pressure for a special load case.

Do You Ever Need A Different Size?

Sometimes, yes. Some trims ship with more than one approved wheel-and-tire package. Winter setups may also use another approved size. But random swaps can throw off speedometer readings, ride height, turning clearance, and braking feel.

If you’re changing wheel diameter, the clean route is to use a fitment calculator, confirm the alternate size in the manual or with a dealer, and make sure the load and speed ratings still meet spec. If you don’t have that confirmation, stick with the placard size.

Use This 5-Minute Check Before You Order

Do these five checks and you’ll dodge most tire-order headaches:

• Open the driver’s door and photograph the placard.
• Write down front size, rear size, and cold pressure.
• Read one current tire to see whether it matches the placard.
• Note the load index and speed rating on your existing tire.
• Check whether your car uses a compact spare or a full-size spare.

That small routine gives you the full tire spec, not just the part people notice first. Once you have that, ordering the right set is straightforward.