How to Read Tire Size: Meaning, Format, and Fitment Guide

Installing the correct tires keeps your vehicle safe and performing as designed. Here’s how to quickly find and understand your tire size so you can choose the right replacements and book installation with confidence.

Where to find your tire size

• Driver’s door placard: The sticker on the driver-side door jamb lists the recommended tire size, load index, and speed rating.
• Owner’s manual: Look in the “Tires” or “Specifications” section.
• Tire sidewall: If your tires are original equipment (OE), the size is molded into the sidewall.

If you prefer a guided match, tell us about your vehicle and driving, and get personalized options with Treadwell.

How to read a common tire size (example: P205/55R16 91H)

• Tire type: The first letter shows type.
• P = Passenger (cars, crossovers, light-duty pickups)
• LT = Light Truck (¾- and 1‑ton pickups, SUVs, full-size vans)
• T = Temporary spare (emergency use only)
• No letter = Euro‑metric passenger tire
• Learn more: Euro‑metric vs. P‑metric
• Width: 205 = section width in millimeters (distance sidewall to sidewall). Details: Section width
• Aspect ratio: 55 = sidewall height as a percentage of width (55% of 205 mm).
• Construction: R = Radial (D = Bias). More on tire construction.
• Rim diameter: 16 = fits a 16‑inch wheel only.
• Load index: 91 = the tire’s max load capacity (use a standardized table). Overview: Load index and load range.
• Speed rating: H = max tested speed capability. Guide: Speed ratings.

Tip: Maintain at least the same load index and speed rating as your vehicle’s placard when you replace tires.

Reading light‑truck and flotation sizes (e.g., 35x12.50R17)

Some off‑road and LT sizes use an inch‑based “flotation” format: - 35 = overall tire diameter (inches) - 12.50 = section width (inches) - R = radial construction - 17 = wheel diameter (inches)

For precise dimensions and conversions, use the Tire Size Calculator.

Fitment and safety tips

• Match the placard: Choose a size that fits your wheel diameter and maintains overall diameter, load index, and speed rating.
• Don’t mix types: Keep all four tires the same size, model, and construction when possible. Staggered setups should stay within OEM spec.
• Check pressure: Proper inflation protects load capacity and wear. Learn how to check tire pressure or stop by for a free air check.
• Know when to replace: See our guide on when to replace tires.

Helpful to know before you buy

• Typical services included with a tire purchase at many tire centers:
• Mounting and balancing
• New rubber valve stems or TPMS service kits (as needed)
• Old tire disposal
• Complimentary rotations, rebalancing, flat repairs, and pressure checks for the life of the tires (varies by retailer and location)

• Optional road‑hazard protection plans are often available at checkout

• Tire manufacture date location:

• Look on the tire sidewall for the DOT code. The last four digits show the week and year of manufacture (for example, “2323” = 23rd week of 2023). The full DOT code may appear on only one side of the tire; you may need to check the inner sidewall.

• Finding 35‑inch tires:

• Search by flotation sizes (e.g., 35x12.50R17) on Shop Tires or enter your vehicle and filter by overall diameter.

• Finding car tires near you:

• Enter your vehicle on Shop Tires and select your closest location, or use the Store Locator to browse in‑stock options and book installation.

• Finding all‑season tires near you:

• Explore in‑stock choices at your local store on our All‑Season Tires page, then schedule installation.

Ready to roll?

• Compare and buy: Shop Tires
• Get personalized matches: Find tires with Treadwell
• Schedule install: Make an appointment
• Find a location: Store Locator
• Save on your set: Current promotions