Where to find your tire size without guessing
Your tire size is printed on the sidewall of every tire on your vehicle. You do not need to remove the tire or use any tools — you can read it while the tire is still on the car. The size appears as a series of numbers and letters, usually in white text, and looks like this: P215/65R15 or LT245/75R16.
If you want the information without bending down to look at the tires, you have three other places to check: your vehicle's door jamb label, your owner's manual, or your vehicle registration documents. Each of these sources will tell you the original tire size your vehicle came with from the factory.
The reason you have multiple sources is that tire size matters for safety and performance. If you replace your tires, you need to match the size the manufacturer specified, or you risk affecting your speedometer accuracy, fuel economy, and how your vehicle handles on the road.
Key Takeaways
- The tire size is printed on the sidewall of each tire in a code like P215/65R15, and you can read it without removing the tire.
- Your vehicle's door jamb label, usually on the driver's side door frame, lists the factory tire size and is often the fastest place to look.
- Your owner's manual and vehicle registration both contain the original tire size specification.
- The numbers and letters in the tire code tell you the width, aspect ratio, construction type, and wheel diameter, which all affect how the tire performs.
Reading the tire sidewall code
The tire size code breaks down into distinct parts, and each one means something specific. The first letter or letters indicate the tire type: P means passenger car, LT means light truck, and T means temporary spare. If there is no letter at the start, it is a metric tire.
The first set of numbers is the tire width in millimeters. In P215/65R15, the 215 means the tire is 215 millimeters wide from sidewall to sidewall. The next number after the slash is the aspect ratio, which is the height of the sidewall as a percentage of the width. An aspect ratio of 65 means the sidewall height is 65 percent of the width.
The letter after the aspect ratio indicates construction type. R means radial, which is standard on all modern vehicles. D means diagonal (bias-ply), which you will rarely see on new tires. The final number is the wheel diameter in inches. A tire coded R15 fits a 15-inch wheel.
Some tire codes include additional information after the wheel diameter. You might see a load index (a number) and speed rating (a letter) that tell you the maximum weight and speed the tire is rated for. These are important if you are replacing tires, because using a tire with a lower rating than the original can be unsafe.
Checking the door jamb label
The door jamb label is a sticker or placard mounted on the inside of your driver's side door frame, usually visible when you open the door. It contains the vehicle's original tire size specification, along with the recommended tire pressure for both front and rear tires (which may differ).
This label is often easier to read than bending down to the tire sidewall, and it is always accurate for the vehicle as it left the factory. If you have replaced your tires with a different size, the label will still show the original size, so you will know what the manufacturer intended.
The label also lists the vehicle's gross vehicle weight rating (GVWR) and other specifications. If you cannot find it on the driver's door frame, check the passenger door frame or the inside of the fuel door — some manufacturers place it in these locations instead.
Using your owner's manual and registration
Your vehicle's owner's manual contains a specifications section that lists the factory tire size. This is useful if you have lost the door jamb label or if it has become illegible from sun damage or wear. The manual also explains what the tire code means and may include guidance on tire replacement and maintenance.
Your vehicle registration documents may also include the tire size, though this is less common. Some states print it on the registration card, while others do not. If you have the paperwork from when you purchased the vehicle, check the bill of sale or the window sticker (Monroney label) — both often list the original tire size.
If you have lost your physical manual, you can usually find a PDF version online by searching for your vehicle's year, make, and model plus the word "manual." Many manufacturer websites and third-party sites host free copies.
What happens if your tires are a different size than the original
If you have replaced your tires with a different size than what the door jamb label shows, your speedometer may read inaccurately. A larger tire will make your speedometer read slower than you are actually going, while a smaller tire will make it read faster. This affects not only your speed awareness but also your odometer reading and fuel economy calculations.
Changing tire size can also affect your vehicle's handling, braking distance, and fuel efficiency. The suspension and steering are calibrated for the original tire size, so a significant change can alter how the vehicle responds. Most manufacturers allow a variation of up to 3 percent in overall tire diameter, but going beyond that is not recommended.
If you need to use a different size temporarily — for example, if your regular size is out of stock — check your owner's manual or contact the tire retailer to see what alternatives are within the acceptable range. Never assume that a tire that physically fits your wheel is the right choice for your vehicle.
Tire size versus wheel size: why they are not the same
Your tire size and your wheel size are two different measurements, and it is straightforward to confuse them. The wheel size is the diameter of the metal rim, measured in inches. The tire size includes the wheel diameter as its last number, but it also includes the width and sidewall height.
When you buy replacement tires, you need to match both the tire size code and the wheel diameter. A tire coded 215/65R15 fits a 15-inch wheel, but a tire coded 215/65R16 fits a 16-inch wheel. If you try to mount a 16-inch tire on a 15-inch wheel, it will not fit, and if you try to mount a 15-inch tire on a 16-inch wheel, it will be too small.
If you have upgraded your wheels to a larger diameter, you will also need to change your tire size to match. A common upgrade is from 15-inch to 17-inch wheels, which requires a different tire code. Your tire retailer can help you find the correct size for your new wheels, but always verify that the new size is within the manufacturer's acceptable range.
Frequently Asked Questions
Can I use a different tire size than what is on the door jamb label?
You can use a different size if it is within 3 percent of the original overall diameter, but this should only be done if necessary. Consult your owner's manual or a tire professional to confirm the alternative size is safe for your vehicle. Using a significantly different size can affect speedometer accuracy, handling, and safety.
What if the tire sidewall is worn and I cannot read the size?
Check your door jamb label, owner's manual, or vehicle registration instead. These sources will always show the original tire size. If you have replaced your tires and do not know the current size, you can measure the tire width and wheel diameter with a ruler or tape measure, though this is less precise than reading the code.
Does the tire pressure listed on the door jamb explore to all seasons?
The pressure on the door jamb is the cold tire pressure recommended by the manufacturer for normal driving. You should check and adjust your tire pressure in cold weather, as pressure drops in winter. Some vehicles have different pressures for summer and winter tires, so check your manual if you use seasonal tires.
Where is the load index and speed rating on the tire code?
The load index and speed rating appear after the wheel diameter. For example, in the code P215/65R15 91H, the 91 is the load index and the H is the speed rating. These indicate the maximum weight and speed the tire can safely handle. Always match these ratings when replacing tires.
What if I have a spare tire — does it have a different size?
Full-size spares are usually the same size as your regular tires. Compact or temporary spares are smaller and are marked with a T in the tire code, like T125/80R16. Temporary spares are meant for short-distance driving only and should not be used as a permanent replacement. Check your owner's manual for the correct spare tire size and pressure.