How to Find Your Car's Tire Size: Sidewall, Door Jamb, Manual and VIN Lookup
Your tire size is recorded in several places, and knowing which one to trust saves time, money and a wasted trip to the tire shop. The tires themselves show what is mounted today, while the door jamb placard and owner's manual show what the manufacturer fitted. VIN and model lookups fill the gaps when a sticker is missing or the sidewall is hard to read.
Where the tire size is printed on the tire sidewall
Every passenger tire has its size code molded into the sidewall, usually in raised characters near the brand and model name, and the same code appears on both the inboard and outboard sides. Front tires are easiest to read if you turn the steering wheel fully to one side, which exposes more of the sidewall. A flashlight held at a low angle makes the raised lettering cast shadows, and wiping away dirt or brake dust with a rag often turns an unreadable string into a clear one.
A code such as P225/60R17 98H reads left to right. The P marks a passenger tire, 225 is the section width in millimeters, and 60 means the sidewall height is 60 percent of that width. R indicates radial construction, 17 is the wheel diameter in inches, 98 is the load index and H is the speed rating. DOT codes, treadwear grades and traction ratings sit nearby, but they describe manufacture and performance, not fit. Light-truck tires may start with LT or use a different layout, so copy the entire string exactly.
Finding the factory size on the door jamb placard and in the owner's manual
The manufacturer's tire and loading information placard is usually on the driver door jamb or the edge of the door itself, visible when the door is open. Some vehicles put it inside the glove box, on the fuel door or under the trunk lid instead. The placard lists the original equipment tire size and the recommended cold inflation pressure, meaning the pressure measured before driving warms the tires. Vehicles with different front and rear sizes show each axle separately, along with separate pressures when those differ.
The owner's manual, usually in the tire and wheel or specifications section, repeats this information and may list several sizes, because the same model can leave the factory with different wheel packages depending on trim. The placard is the authoritative reference for what the manufacturer actually fitted to your vehicle, while the sidewall only tells you what someone mounted most recently. Check the spare separately too, since temporary spares often use a different size and a higher pressure than the road tires, and the placard or manual typically lists the spare on its own line.
Looking up tire size by VIN, year and model, or with a tire finder tool
A vehicle identification number encodes the year, make, model and often the trim level, so a retailer or manufacturer database can use it to return the original equipment tire size. Online tire finders work the same way when you enter year, make, model and trim by hand. Trim matters more than many owners expect, because a base sedan and a sport version of the same car may ship on different wheel diameters, and picking the wrong trim in a dropdown can produce a size that does not match your wheels.
Many tire finders also work in reverse: enter a known size to see which tires are sold in that dimension, then use the load index and speed rating filters to exclude any that fall below your vehicle's requirement. Keep in mind that a lookup may return several possible sizes rather than one answer, especially for models with optional wheel packages. Confirm the result against the door placard or the tires on the car, and if online tools disagree, a dealership parts department can usually confirm the factory size directly from the VIN.
Step by step: checking the size of the tires currently on your car
Before buying replacements, read the sidewall on all four tires and write down each full string, not just the first few numbers. Then compare those notes with the placard. On most vehicles all four should match, but some performance and luxury models use a staggered setup with wider or different-diameter rear tires, and the placard will show that. If one tire differs from the others while the placard lists a single size, a mismatched replacement was probably installed at some point and should be corrected.
Pay attention to the load index and speed rating at the end of the code. A replacement should meet or exceed the values specified for the vehicle, because a lower load index reduces how much weight each tire is designed to carry and a lower speed rating reduces its rated capability. Common mistakes include mixing up the wheel diameter with the section width or misreading a worn character, such as taking an 8 for a 6. Photographing each sidewall lets you zoom in later and double-check without crawling back under the fender.
How tire size is measured and what to do when the sidewall is unreadable
Each part of the code refers to a specific dimension. Section width is measured across the widest point of the tire's sidewalls, excluding raised lettering or protective ribs. The aspect ratio expresses sidewall height as a percentage of that width, so the same ratio produces a taller sidewall on a wider tire. Rim diameter refers to the bead seat, where the tire seals against the wheel, not the outer lip you see from the side. That is why tape-measuring the visible edge of a wheel usually reads larger than the marked size.
If a tire is missing or its markings are worn away, you can estimate wheel diameter by measuring across the bead seats with a tape, but treat the result as a check rather than an answer. Width on a mounted, inflated tire changes with rim width and pressure, so a tape cannot reliably identify section width. Two tires with different codes can also share nearly the same overall diameter and rolling circumference. Whenever the placard, a matching tire on the car or a VIN lookup is available, rely on that instead of a tape.
Quick reference: the fastest ways to find your own tire size
For most owners the quickest route is the door placard first, then the sidewall of the current tires, then the owner's manual, and finally a VIN or model lookup if the other sources are missing or unclear. Before shopping or calling a shop, write down the full size code, the load index, the speed rating and whether front and rear sizes differ. If the tires on the car do not match the placard, a previous owner may have installed different wheels or chosen a plus size, but the placard remains the baseline.
Bring in a tire shop or dealer when the tires on the car disagree with each other, when the vehicle wears aftermarket wheels, or when the placard is missing, faded or damaged. These are the situations where a quick online answer is most likely to be wrong. Staying close to the original size matters because overall diameter affects speedometer and odometer readings, larger tires can rub against suspension or body parts, and load capacity must suit the vehicle's weight. Any change from the factory size deserves a professional review before you buy.