How can I tell what size tires I have?
You can tell by reading the tire sidewall for the exact size (for example, P215/65R15) and by checking your vehicle’s door placard or owner's manual for the recommended size. These sources usually agree, but the sidewall shows the tires currently on your car.
In most passenger cars, the installed tire size is printed on the sidewall of each tire, while the vehicle manufacturer provides the recommended size on a placard located on the door frame or in the owner's manual. If you see different sizes on the front and rear tires, each axle may have a specific specification, and you should follow the OEM guidance for replacement. The following sections explain how to read the markings and where to look for official guidance.
Read the tire sidewall to identify the installed size
The sidewall inscription is the quickest way to confirm the exact size on each tire. It may vary if your vehicle runs different sizes on different wheels, so check all tires to be sure.
Decoding a typical size inscription
- Type code: The first letter or letters indicate the tire category, e.g., P for passenger car or LT for light truck. Some temporary spares use a T.
- Width: The three-digit number (e.g., 215) is the tire width in millimeters from sidewall to sidewall.
- Aspect ratio: The two-digit number after the slash (e.g., 65) is the sidewall height as a percentage of the width.
- Construction: The letter after the aspect ratio (usually R) shows the tire’s construction type (R = radial is standard for most modern tires).
- Wheel diameter: The two-digit or two- or three-digit number after the construction letter (e.g., 15) indicates the wheel diameter in inches.
- Load index and speed rating: Optional codes after the size (e.g., 95H) specify load-carrying capacity and maximum speed.
Concluding: The full sidewall sequence (for example, P215/65R15 95H) provides the installed size plus performance ratings. If you’re unsure about any part of the inscription, a tire shop can interpret it for you or verify compatibility with your vehicle.
Where to locate the official size for replacement
To ensure you buy the correct tires, verify the manufacturer’s recommended size from official sources. This helps preserve handling characteristics, ride quality, and safety features.
Key sources for the recommended size
- Door placard: Found on the driver’s side door jamb or inside the fuel filler door. It lists the Original Equipment (OE) tire size and pressures.
- Owner's manual or maintenance guide: Provides the recommended tire size, load index, speed rating, and any approved alternatives.
- Spare tire label: Some vehicles place the spare size on the spare tire itself or in the trunk; use this if you must replace the spare temporarily.
- Manufacturer websites or dealership: If you don’t have the manual, you can look up the vehicle by VIN or model to obtain the official tire specifications.
Concluding: Always cross-check the installed tires with the official recommended size before purchasing replacements, and beware any restrictions such as run-flat requirements or unique OEM configurations.
Practical considerations when replacing tires
When considering replacements, it’s important to understand how size choices affect performance, safety systems, and warranty considerations.
Common scenarios and guidance
- Keep sizes consistent on all wheels: In most cases, use the same size on every wheel. If you must mix sizes, the difference can affect speedometer accuracy, ABS/traction control performance, and ride feel.
- LT vs P tires: LT (Light Truck) tires have higher load-carrying capacity and are used on pickups and larger SUVs. If your OE is a P tire, switching to LT may require professional guidance to avoid clearance or performance issues.
- Maintain similar overall diameter: Try to keep the overall diameter within about 3% of the original. A large deviation can affect speedometer readings, traction control, and the vehicle’s stability systems.
- Rim compatibility and clearance: Ensure the chosen tire width and rim diameter fit your wheels and don’t rub on fenders, brakes, or suspension components.
Concluding: If you’re upgrading to a different size, consult a tire professional to confirm compatibility with your vehicle’s systems, load requirements, and warranty terms.
Summary and quick reference
To quickly determine your tire size, read the sidewall inscription (width/aspect ratio/construction/diameter and, if present, load index and speed rating) and cross-check with the door placard or owner's manual for the recommended size. For replacements, use the OEM-specified size unless a professional approves an alternative that preserves safety and performance, keeping overall diameter in a reasonable range. Regularly check tire pressures and inspect tread wear to maintain safety on the road.
How do I tell what size tires I have?
You can tell what size tires you have by checking the sidewall of the tire for a code like P215/65R15, or by looking at the sticker on the driver's side door jamb for the manufacturer's recommended size. Other places to check include the owner's manual, glove box, or fuel filler door.
This video explains how to find your tire size: 55sManiZillaYouTube · Mar 10, 2019
On the tire's sidewall
Look for a code that includes a series of numbers and letters, such as P215/65R15. Here's what each part means:
- P (or LT, ST, etc.): Indicates the tire type, such as P for passenger vehicle.
- 215: The width of the tire in millimeters, from sidewall to sidewall.
- 65: The aspect ratio, which is the height of the tire's sidewall as a percentage of its width.
- R: The construction type, with "R" indicating a radial tire.
- 15: The diameter of the wheel in inches that the tire fits on.
On your vehicle
- Door Jamb Sticker: Open the driver's side door and look for a sticker on the door frame or jamb. It will have the original equipment (OE) tire size.
- Owner's Manual: Check the manual for your car's specifications.
- Other locations: Some vehicles have a sticker with tire information inside the glove box door, on the fuel filler door, or in the center console.
How do I find out my tire size?
Every tyre carries a code on the sidewall that tells you its width, profile, rim diameter, load capacity and speed rating. Understanding these details is important when choosing replacements, as fitting the wrong size can affect handling and safety, as well as fuel efficiency.
Can I look up tire size by VIN number?
No, a VIN number does not typically contain tire size information directly, but you can use a VIN lookup tool on many automotive websites to find the original equipment (OE) tire size for your vehicle's specific make, model, and trim. Other reliable methods include checking the sticker on your driver's side door jamb, your owner's manual, or the sidewall of your current tires.
Ways to find your tire size
- Use a VIN lookup tool: Many websites, such as AutoZone, CARFAX, and Discount Tire, have VIN decoders that will provide your vehicle's specific trim and tire size.
- Check the driver's side door jamb: This is the most common place to find a sticker with the original equipment tire size and recommended pressure.
- Read your owner's manual: Your vehicle's manual will contain the recommended tire size for your specific model and trim.
- Look at your current tires: The size is printed on the sidewall of your current tires, but be aware this may not be the original size if the tires have been changed.
- Search online for your vehicle's make, model, and trim: This will help you find the correct specifications, as different trims of the same car can have different tire sizes.
How to tell how tall a tire is?
You can find a tire's height by using the numbers on its sidewall to calculate the total diameter, or by physically measuring the tire from the ground to its highest point with a tape measure. To calculate, decode the size (e.g., P205/60R16) where 205 is the width, 60 is the aspect ratio (sidewall height is 60% of the width), and 16 is the rim diameter in inches.
Using the tire's sidewall information
- Find the tire size: Look on the sidewall for a sequence like P205/60R16.
- Identify the width: The first number is the section width in millimeters (e.g., 205).
- Find the aspect ratio: The second number is the aspect ratio (e.g., 60).
- Calculate the sidewall height: Multiply the width by the aspect ratio as a decimal.
- 205 mm×0.60=123 mm205 mm cross 0.60 equals 123 mm205 mm×0.60=123 mm
- Find the rim diameter: The number after the "R" is the wheel diameter in inches (e.g., 16).
- Convert measurements: Convert the rim diameter from inches to millimeters:
- 16 inches×25.4=406.4 mm16 inches cross 25.4 equals 406.4 mm16 inches×25.4=406.4 mm
- Calculate the total diameter: Add the two sidewall heights (which are the same) and the rim diameter.
- 123 mm+123 mm+406.4 mm=652.4 mm123 mm plus 123 mm plus 406.4 mm equals 652.4 mm123 mm+123 mm+406.4 mm=652.4 mm
- Convert to inches (optional): To get the final height in inches, you can divide the total millimeters by 25.425.425.4 or perform a similar calculation using inches.
Using a physical measurement
- Park on a level surface: Ensure the vehicle is on a flat, level area to avoid inaccurate readings.
- Use a tape measure: Place the tape measure or caliper on the ground and extend it to the very top of the tire's tread.
- Take multiple readings: For accuracy, measure the tire on a couple of different sides and take the average to ensure consistency.
- Compare with specs: It's a good practice to cross-check your physical measurement with the specs on the sidewall to verify accuracy.
