Find your tire size on the sidewall, the driver’s door sticker, the owner’s manual, or the vehicle tire placard.
You don’t need a tape measure, a decoder app, or a trip to the tire shop to find your tire size. In most cases, the answer is already printed on the tire and on the vehicle.
The fastest place to start is the sidewall of the tire that’s on the car now. You’ll usually see a code such as P225/65R17 102H. That string tells you the width, sidewall ratio, construction type, wheel diameter, load rating, and speed rating. If the tire on the car isn’t original, check the driver’s door placard next. That sticker tells you what the vehicle maker wants you to run.
If you’re replacing tires, matching the full size code matters. A tire that “looks close” can still throw off ride height, clearance, speedometer reading, and load capacity. So let’s sort out where to look and what the numbers mean.
Getting Your Tire Size From The Sidewall And Placard
There are four good places to find the right size. Start with the tire, then confirm it on the car.
- Tire sidewall: Best for a fast read when the current tires are known to fit well.
- Driver’s door jamb placard: Best for the factory size and cold tire pressure.
- Owner’s manual: Handy if the sticker is faded or missing.
- Fuel door, glove box, or trunk labels: Some vehicles place tire data there.
Reading The Sidewall Code
Take a common code like P225/65R17 102H. It looks messy at first glance, but it reads left to right in a clean pattern. Once you know that pattern, you can spot tire size in seconds.
The first chunk, P225, gives the tire type and width. The next number, 65, is the aspect ratio. The R means radial construction. Then 17 tells you the wheel diameter in inches. The last bit, 102H, covers load index and speed rating.
What Each Part Tells You
Here’s the plain-English version. P means passenger tire. 225 means the tire is 225 millimeters wide. 65 means the sidewall height is 65% of the width. R means radial. 17 means it fits a 17-inch wheel. 102 is the load index. H is the speed symbol.
If you want a clean visual from a tire maker, Bridgestone’s tire size explainer shows the same sequence and how each part is read.
Using The Vehicle Placard
The placard is often the tie-breaker. Open the driver’s door and look on the jamb, door edge, or pillar. You’ll usually see the original tire size, spare tire size if the vehicle has one, and the cold inflation pressure for front and rear tires.
This matters when the current tires were changed by a previous owner. A car may be riding on the wrong size and still look fine to the eye. The placard gives you the factory fitment, which is the safest place to begin when you’re buying replacements.
What The Numbers In A Tire Size Mean
Once you can read the code, shopping gets easier. You can compare what’s on the tire with what’s on the placard and spot mismatches right away.
| Code Part | What It Means | Sample Read |
|---|---|---|
| P | Tire type | Passenger vehicle tire |
| LT | Tire type | Light-truck tire |
| 225 | Section width | 225 mm wide |
| 65 | Aspect ratio | Sidewall height is 65% of width |
| R | Construction | Radial tire |
| 17 | Wheel diameter | Fits a 17-inch wheel |
| 102 | Load index | Load capacity class for that tire |
| H | Speed symbol | Rated for a set top-speed class |
You may also see extra marks such as M+S, a mountain-and-snowflake symbol, or XL for extra load. Those marks matter when you’re matching tire type, but the core size still comes from the main code.
How To Get Tire Size When The Old Tires Are Gone
If the car has no tires, the sidewalls won’t help. That’s when the placard and the owner’s manual do the heavy lifting. Start with the driver’s door sticker. If it’s missing, check the manual’s tire and loading section. Many manuals list more than one approved size, tied to trim level or wheel package.
Places To Check On The Vehicle
When the door sticker is gone or unreadable, work through these spots:
- Driver’s door jamb: Most common location.
- Fuel filler door: Seen on some cars and crossovers.
- Glove box or center console: Less common, but worth a look.
- Spare tire area: A label may list spare and road-tire specs.
- Owner’s manual: Good backup when stickers are missing.
You can also match the placard size with the ratings shown on the sidewall. NHTSA’s tire safety page explains that passenger tires carry sidewall markings and government ratings that help identify what you’re buying.
What To Match Beyond The Main Size
The width, ratio, and wheel diameter get most of the attention, but don’t stop there. The load index and speed symbol should meet or beat the vehicle maker’s spec. If you drop below the required load or speed class, the tire may not be a proper replacement even if the size looks right.
Also watch for front and rear differences. Some cars run a staggered setup, with wider rear tires than front tires. If you order four of the same size on a vehicle like that, you’re going to have a bad afternoon.
| Where You Found It | Best Use | Watch For |
|---|---|---|
| Current tire sidewall | Fast read of what is mounted now | May be a non-factory size |
| Door placard | Factory tire size and pressure | Can be faded or missing |
| Owner’s manual | Backup source with trim notes | May list more than one approved setup |
| Spare tire label | Checks spare size and limits | Not always the same as road tires |
| Wheel itself | Confirms diameter only | Does not confirm full tire size |
Mistakes That Lead To The Wrong Tire Size
Most tire-size mix-ups come from reading only part of the code or trusting what’s already on the car. These are the slip-ups that cause the most trouble:
- Reading only the last number: A 17-inch wheel can take many tire sizes. The diameter alone is not enough.
- Skipping load index and speed symbol: The tire may fit the wheel but still miss the vehicle spec.
- Trusting worn or modified setups: Lift kits, lowering springs, or aftermarket wheels change what fits cleanly.
- Mixing metric and inch-based readings: Tire width is usually metric, wheel diameter is usually inches.
- Ignoring front/rear differences: Some cars need two sizes, not one.
If the code on the tire and the code on the placard don’t match, use the placard and manual as the better starting point. Then check wheel size and brake clearance before you buy.
A Simple Way To Double-Check Before You Buy
Use this quick routine. Read the full code on the current tire. Read the placard on the driver’s door. Match the width, aspect ratio, construction, wheel diameter, load index, and speed symbol. Then match the cold tire pressure listed on the placard after the new tires are installed.
If the old tires are gone, the placard and manual usually give you the answer. If the vehicle has more than one approved size, pick the one tied to the wheel diameter already on the car. That keeps the fit clean and cuts down on guesswork.
So, if you’re trying to get tire size in a hurry, read the sidewall first and confirm it on the placard. That two-minute check can spare you a wrong order, a return trip, and a set of tires that never should’ve left the warehouse.
References & Sources
- Bridgestone Americas.“How to Read & Determine Tire Size for Your Vehicle.”Shows how to read the sidewall code, including width, aspect ratio, construction, wheel diameter, load index, and speed symbol.
- National Highway Traffic Safety Administration (NHTSA).“Tire Safety Ratings and Awareness.”Shows what appears on passenger-tire sidewalls and explains the government tire ratings found there.