To see what size tires you have, read the sidewall code or the driver-door placard and match width, aspect, and wheel diameter.
Shopping for tires starts with one task: learn how to see what size tires you have. You can read the code molded into the tire sidewall, or check the tire information placard on the driver door opening. Both show a string such as P225/60R17 99H. That string holds the width, aspect ratio, construction, wheel diameter, load index, and speed symbol. This guide shows quick ways to find that string, decode it, and avoid mix-ups when trims or wheel packages change the spec.
Fast Ways To Find Tire Size On Your Vehicle
Start with these checks. Verify using more than one source if the vehicle has custom wheels or a temporary spare.
| Where To Look | What You See | When To Trust It |
|---|---|---|
| Tire Sidewall | Complete size like P215/65R17 98H; brand and model nearby | Use for the tire that is mounted; cross-check at each corner |
| Driver-Door Placard | OE size and cold pressure for front, rear, and spare | Best baseline for stock wheels; required by FMVSS 110 |
| Owner’s Manual | Approved sizes and notes for trims and tow packages | Good reference when wheels were changed by a prior owner |
| Fuel Door Or Glovebox Label | Pressure and sometimes the original size | Useful on some imports and crossovers |
| Spare Tire | T-type temporary spare size, often narrower and smaller | Do not match this size to your main tires |
| Build Sheet/VIN Lookup | Factory wheel and tire package codes | Helpful for trucks and SUVs with multiple packages |
| Service Records | Previous size changes or upsized wheel notes | Use to spot non-stock changes that need extra checks |
The tire information placard on the driver door opening is a legal label in the United States for most passenger vehicles. It lists the original tire size and the cold pressures. You can review the rule in FMVSS 110. For sidewall terms and the DOT code, the NHTSA tire guide gives diagrams.
How To See What Size Tires You Have On The Sidewall
Use an example size: P225/60R17 99H. The first letter shows the service type. “P” means a passenger tire built to Tire and Rim Association rules. “LT” marks a light-truck fit with different load formulas. A code with no letter at the start is a Euro-metric passenger size. Some off-road tires use a flotation format such as 31×10.50R15LT.
Read Width, Aspect Ratio, And Construction
The three-digit number after the letter is the section width in millimeters. Next comes the two-digit aspect ratio. That is the sidewall height as a percentage of the width. The letter after the slash shows construction. “R” is radial, which is the norm on modern road tires.
Match Wheel Diameter
The number after the construction letter is the wheel diameter in inches. That must match the wheel bolted to the hub. If your vehicle has multiple wheel options across trims, the door placard lists the diameter that came with your VIN at the factory.
Check Load Index And Speed Symbol
The last two parts are the load index and the speed symbol. Load index is a two- or three-digit code that maps to a weight the tire can carry. The speed symbol is a letter such as T, H, V, W, or Y. Match or exceed the original ratings from the placard when you buy replacements.
Close Variant: See Your Tire Size Quickly And Avoid Mix-Ups
Wheel and tire packages can change across trims. A base model may run a taller sidewall on a 16-inch wheel. A sport trim may step up to an 18-inch wheel with a lower aspect ratio to keep the overall diameter close. That is why a quick check across all four corners helps. A mismatched spare or an upgrade on only the rear axle can hide the true spec.
When The Sidewall Size And Door Placard Do Not Match
Start by learning which item changed: the wheel or the tire. If the vehicle now wears larger wheels, the current tire size will differ from the placard but still fit the wells if the overall diameter stayed near stock. If the placard calls for P225/60R17 and the current set shows 235/55R18, that is a common plus-one swap with a similar outside diameter.
Spare Tire And Winter Set Exceptions
Temporary spares and winter packages can be narrower. A T125/70D16 spare is intended only for short use. A winter set may drop one wheel size to gain more sidewall and snow grip. In both cases, rely on the current tire sidewall for the exact size while matching or exceeding the original load index and speed symbol.
Decode Each Part Of A Tire Size
Use this quick decoder as you read the sidewall on your vehicle. The same pattern appears on all four tires. If one shows a different size, treat that as a red flag and measure the outside diameter to confirm clearance before long trips.
Passenger And Light-Truck Markings
“P” means a passenger tire size. “LT” ahead of the width marks a light-truck design. “T” marks a temporary spare. Many commercial van sizes show a “C” suffix with load range data. The DOT code on the sidewall also reveals the week and year the tire was built.
Aspect Ratio And Ride
Lower aspect ratios lead to a shorter sidewall. That can sharpen steering at the expense of ride plushness. A higher aspect ratio adds cushion. Staying near the original outside diameter keeps gearing and speed readings stable.
Load Index And Speed Symbol Basics
Load index numbers climb with capacity. A 94 code maps to 670 kg (1,477 lb). A 99 code maps to 775 kg (1,709 lb). The speed symbol maps to a tested speed under load on a lab drum. Match your original spec. Many shops will refuse to install a tire with a lower service description than stock.
Tire Size Examples And What They Mean
| Printed Size | What It Tells You | Notes |
|---|---|---|
| P225/60R17 99H | Passenger tire, 225 mm width, 60% aspect, 17-inch wheel, load 99, speed H | Common midsize sedan fitment |
| 225/40R18 92Y | Euro-metric passenger size with no prefix; low profile | Often on sport packages |
| LT245/75R16 E | Light-truck tire, 245 mm width, 75% aspect, 16-inch wheel, Load Range E | High load capacity for towing |
| 31×10.50R15LT | Flotation size, about 31 inches tall, 10.5 inches wide, radial, 15-inch wheel | Common off-road fit |
| T125/70D16 96M | Temporary spare, 125 mm width, 70% aspect, 16-inch wheel, bias-ply | Short-distance use only |
| 235/65R18 106H | Passenger SUV size with higher load index | Frequent on crossovers |
| 275/55R20 113T | Passenger truck size with 20-inch wheel | Often paired with large OEM wheels |
Step-By-Step: Verify Tire Size With Zero Guesswork
1) Clean And Read The Sidewall
Turn the steering wheel to expose the front sidewall. Wipe the area with a damp cloth. Capture a photo so you can zoom. Confirm the full size string includes the load index and speed symbol.
2) Check The Driver-Door Placard
Open the driver door and find the yellow and white placard. Note the tire size for front, rear, and spare along with the pressure targets. Cars and light trucks sold in the U.S. must display this label.
3) Match Wheel Diameter And Bolt Pattern
Peek through the spokes and confirm the stamped wheel size. It may appear on the back face of one spoke. If the wheels are aftermarket, match the printed wheel diameter to the tire size and verify brake clearance.
4) Confirm Load Index And Speed Symbol
Cross-reference the two- or three-digit load index to a capacity chart and confirm it meets or exceeds the placard. Match the speed symbol to the same or a higher letter than stock.
5) Repeat On All Four Tires
Check each corner. Mix-and-match sets happen during emergency replacements. A set with one odd size can pull the car or trip ABS and AWD systems.
How To See What Size Tires You Have For Special Cases
Plus-Sizing And Minus-Sizing
When moving to a larger wheel, the new tire gets a lower aspect ratio so the outside diameter stays similar. This keeps speed readings steady. A minus-size winter set does the reverse to gain more sidewall and traction in snow. In both cases, verify brake clearance and keep the load index at or above stock.
All-Wheel-Drive And Staggered Setups
Many AWD systems expect all four tires to match circumference within a small range. A staggered rear-wheel-drive setup uses wider rears on the same overall diameter. Read each sidewall. Record front and rear sizes as a pair to avoid ordering four identical tires by mistake.
Trailers, Light Trucks, And Load Range
LT sizes use load ranges such as C, D, or E that map to ply ratings and max pressure. Trailer ST sizes have their own service limits. Match the specification to the load you tow and the wheel rating.
Finish With A Safe Order
By now you know how to see what size tires you have from the sidewall and the placard. Save the size string in your phone along with the load index and speed symbol. When you order, match all three across a full set. You will land on the correct fit, clean handling, and a smooth ride.