Knowing your tire size is essential when buying replacements — and it's easier than most drivers think. The information is printed right on the tire sidewall in a standardized alphanumeric code.
Your tire size appears in two places: stamped on the sidewall of every tire on your car, and on a sticker inside your driver's door jamb. The door jamb sticker is the most reliable source — it lists the size your vehicle manufacturer recommends, along with the correct inflation pressure.
A standard size looks like this: P215/65R15. Breaking it down: P = passenger vehicle type, 215 = section width in millimeters, 65 = aspect ratio (sidewall height as % of width), R = radial construction, 15 = wheel diameter in inches. Some tires also include a load index and speed rating after the diameter (e.g., 95H).
The three-digit section width (e.g., 215) tells you how wide the tire is from sidewall to sidewall. A wider tire generally provides more contact patch area, which can improve cornering grip. The two-digit aspect ratio (e.g., 65) describes the sidewall's height relative to the width — a lower number means a shorter, sportier sidewall. The wheel diameter (e.g., 15) must exactly match your rim.
