How To Know What Size Tires I Have | Read The Code Right

Check the sidewall for a code like 225/65R17, then match it to the driver’s door sticker to confirm the right fit.

Tire size looks dense at first glance, yet it gets easy once you know where each number lives and what job it does. You do not need a shop scanner or a lucky guess. In many cases, you can confirm the right size in under five minutes with a clear method.

Start with the tire itself and the placard on your vehicle. Those two spots tell you the size now on the car and the size the vehicle maker picked for that model. When they do not match, you can spot that before you spend money on the wrong set.

How To Know What Size Tires I Have From The Sidewall And Door Sticker

Use these checks in order.

• Read the full size code molded into the tire sidewall.
• Check the driver’s door jamb sticker for the factory tire size and cold pressure.
• Compare front and rear tires in case your car uses different sizes.
• Check the spare on its own. A compact spare often uses a different size.
• Match load index and speed rating when you buy replacements, not just the width and rim size.

Start With The Tire Sidewall

Every road tire has a size string stamped into the sidewall. It often looks like this: P215/60R16 94H. That line gives you width, sidewall shape, construction type, wheel diameter, load index, and speed symbol. If the sidewall is dusty, wipe it off and scan around the outer edge.

Do not stop at the last number you notice. Many drivers see only the “16” or “18” and assume that is the full size. Wheel diameter is only one part of the fit.

Then Check The Door Jamb Sticker

Your next stop is the tire placard, usually on the driver’s door jamb, door edge, glove box, or trunk area. The tire information placard lists the size the vehicle maker approved, along with cold inflation pressure. That sticker is the better reference point when you want the right replacement size for daily driving.

If the sidewall and sticker match, you’re done. If the tire on the car is different, the sticker still tells you what the vehicle left the factory with. That matters when a past owner changed wheel size, fitted a winter set, or used a different tire after a sale.

On some cars, the front and rear tire sizes are not the same. Read both axles before you order. Sports sedans, coupes, and some performance SUVs may use a wider rear tire, and that changes what you need to buy.

What The Numbers And Letters Mean

Once you split the code into chunks, it starts to read like a label, not a puzzle. Tire sidewall markings follow the same basic pattern across mainstream passenger tires.

Here’s how the common parts break down.

Code Part	What It Means	What You Should Do With It
P	Passenger tire class	Match the tire type your vehicle uses unless the placard states a different class.
215	Tire width in millimeters	Use it to compare one tire to another; wider is not always better for stock wheels.
60	Aspect ratio, or sidewall height as a share of width	A lower number means a shorter sidewall and a different overall tire height.
R	Radial construction	Nearly all modern passenger tires use this.
16	Wheel diameter in inches	This must match your wheel size exactly.
94	Load index	Use a replacement tire that meets or exceeds the required load capacity.
H	Speed symbol	Stay at or above the vehicle maker’s minimum rating.
M+S or 3PMSF	Snow service marking	Useful when you are checking if a tire is all-season or severe-snow rated.

Read The Code Left To Right

Take the sample size 225/65R17 102H. The tire is 225 millimeters wide. Its sidewall height is 65 percent of that width. It uses radial construction and fits a 17-inch wheel. Then 102H tells you the load and speed class tied to that tire.

Watch For Extra Letters

You may also see letters like LT for light truck or XL for extra load. If your current tire says LT and the placard says P-metric, trust the placard unless you know the vehicle was set up for a different use.

When The Tire On The Car Does Not Match The Sticker

The tire mounted on the car is not always the right reference. Someone may have changed the wheels, fitted a plus-size package, or mixed sizes across the axles.

Check for these situations before you buy anything:

• Aftermarket wheels: The car may now run a larger wheel and a shorter sidewall tire.
• Staggered fitment: Some cars use one size in front and another in the rear.
• Winter package: A winter set may be narrower than the warm-weather set.
• Temporary spare: The spare can look nothing like the main tires.
• One odd replacement: A single tire may have been replaced with a close, yet wrong, size.

If your current tires differ from the sticker, use the placard as your home base unless you know the full wheel-and-tire package was changed on purpose and set up correctly.

Where To Check	What You’ll Find	Best Use
Tire sidewall	Current mounted tire size and service description	Use it to identify what is on the car right now.
Driver’s door sticker	Factory-approved size and cold pressure	Use it to buy stock replacement tires.
Owner’s manual	Trim-level tire specs and pressure details	Use it when the sticker is worn or missing.
Spare tire sidewall	Temporary or full-size spare markings	Use it to avoid mixing a spare size with your normal set.
Front and rear tires	Possible staggered sizes	Use it to confirm whether all four tires match.
DOT code area	Build week and year at the end of the code	Use it to check age when buying a used set.

How To Check Winter Tires, Spares, And Older Cars

Winter tires can throw you off if you only check what is mounted during one season. Many winter sets use a smaller wheel or a narrower tire than the summer or all-season setup.

Spare tires need their own check. A temporary spare often uses a narrow tire with a compact wheel and a speed limit printed on the sidewall. Do not use that size as your shopping size for a full replacement set.

On older cars, the sticker may be gone or unreadable. In that case, read all four sidewalls, then cross-check the owner’s manual. If the manual lists more than one approved size, match the one tied to your wheel diameter. A car that came with 17-inch and 18-inch wheel packages may use two valid tire sizes, and both can be right for that trim.

Mistakes That Lead To The Wrong Tire Size

Most tire-size mistakes come from rushing or reading only part of the code:

• Buying by wheel diameter alone.
• Ignoring the load index and speed symbol.
• Copying the spare tire size.
• Reading one tire and assuming all four match.
• Missing a staggered front-rear setup.
• Using the current tire size when the vehicle sticker says the car was changed from stock.

Read the full sidewall, check the sticker, and compare both before you order.

A Clean Way To Confirm Before You Buy

Here’s the no-stress method. Read the sidewall on the tire now on the car. Check the driver’s door sticker. Make sure front and rear sizes match, unless the car is built for staggered tires. Then match width, aspect ratio, construction, wheel diameter, load index, and speed symbol.

Once you’ve done that, you know what size is mounted, what size the vehicle maker approved, and whether a seller listing is the real match. That saves you from ordering a tire that fits the wheel yet throws off ride height, clearance, or load capacity.