Your tire size lives in four places: the tire sidewall itself (current tire), the driver’s door jamb sticker (factory spec), the owner’s manual (sometimes with alternative sizes), and your vehicle records (online or in service paperwork). Which one you trust depends on what you’re trying to do — replacing the current tire, returning to factory spec, or checking what’s allowed.
For most replacement decisions, the sidewall and the door jamb sticker are the two you’ll use. The sidewall tells you what’s mounted right now. The door jamb tells you what the manufacturer specified. If they match, you have factory-original sizing. If they don’t, somebody plus-sized at some point.
This guide covers each location and how to read what you see.
1. The Tire Sidewall (Current Tire)
The most direct source: just look at the tire that’s mounted on your vehicle. The size is molded into the outer sidewall in raised lettering.
- Find a clear, unobstructed area of the sidewall — usually on the outboard side (the side facing away from the vehicle).
- Look for a string that looks like: 225/65R17 102H, P215/55R17 94V, or LT265/70R17 121S
- The first 3 digits (225, 215, 265) are the tire width in millimeters.
- The next 2 digits after the slash (65, 55, 70) are the aspect ratio — the height of the sidewall as a percentage of the width.
- The R is the construction type (radial). Almost all modern tires are R.
- The next 2 digits (17, 17, 17) are the wheel diameter in inches.
- The last 2-3 digits and letter (102H, 94V, 121S) are the load index and speed rating.
The sidewall is authoritative for the tire currently mounted. But it doesn’t tell you whether that’s the correct size for the vehicle — a previous owner could have plus-sized or downgraded.
2. The Driver’s Door Jamb Sticker
This is the manufacturer-specified size for your vehicle — the authoritative reference for what the vehicle was designed for.
- Open the driver’s door and look at the B-pillar (the metal pillar between the front and rear doors). Sometimes the sticker is on the door itself or the door frame.
- The placard lists the tire size for both front and rear (often the same; on some vehicles different), the cold tire pressure, the spare tire size and pressure, and the vehicle’s max combined weight.
- The size will match the same pattern as the sidewall (e.g., P225/65R17).
Use this when:
- You’re replacing tires and want to confirm you’re putting on factory-spec size.
- You suspect someone has changed the tire size from stock.
- You’re buying a used vehicle and want to verify it has the right tires.
3. The Owner’s Manual
The owner’s manual section on tires and wheels lists the original size plus, on many vehicles, alternative sizes that are approved for use.
- Look in the “Specifications,” “Maintenance,” or “Tires and Wheels” section.
- Many manuals list multiple approved sizes — the standard size plus optional sizes for different trim levels, plus optional winter sizes for vehicles where the manufacturer specifies different winter tires.
- Some manuals list the spare tire spec separately (compact spares have different sizes and pressure specs).
The owner’s manual is useful when you’re considering plus-sizing — it tells you which sizes the manufacturer has tested and approved for your vehicle.
4. Vehicle Records (Online or Paperwork)
- Manufacturer’s website — most manufacturers have a “tire fit guide” or “specs” tool that takes your VIN or year/make/model/trim and returns the correct tire size.
- Tire shop databases — TireRack, Discount Tire, Tire Buyer, and others have searchable databases that return the approved sizes for your specific vehicle.
- Original purchase paperwork — if you have the original sticker or window decal from when the vehicle was new, the OEM tire size is listed there.
These sources are useful when the door jamb sticker is missing, damaged, or you’re researching alternatives. Manufacturer websites and reputable tire shop databases are reliable; random Internet forums are not (people frequently report fitments that didn’t actually work).
When the Sidewall and Door Jamb Don’t Match
If the size on your current tires doesn’t match the door jamb, somebody changed the tire size at some point. A few possibilities:
- Plus-sized for cosmetic reasons — usually a wider tire on a larger wheel. May rub, may affect speedometer accuracy.
- Downsized for snow performance — narrower winter tires on smaller wheels for better snow traction.
- Approved alternative from the owner’s manual — some vehicles have multiple OEM-approved sizes that fit fine.
- Mismatch error — sometimes installers grab the wrong tire or someone bought the wrong size online. Worth checking against the door jamb when you replace.
For your next replacement, the door jamb is the safer default unless you have a specific reason to deviate.
Bottom Line
Four places to find your tire size: the sidewall (what’s on it now), the driver’s door jamb (factory spec), the owner’s manual (with alternatives), and online vehicle records (cross-check). For most replacement decisions, the door jamb is the authoritative source — that’s the size your vehicle was designed for.
If you only check one place, check the door jamb. It tells you not just the tire size but also the correct pressure for each axle and any vehicle-specific notes that matter for tire choice.
