How to read your tire size
What the numbers on the sidewall mean, and where to find the size your car needs.
Where to find it
Your tire size is molded into the sidewall of every tire. It looks like P225/65R17 102H.
The size your car was built for is also printed on the sticker inside the driver door, and in the owner's manual. If the tires on the car are a different size from the sticker, go with the sticker.
225: the width
The first number is the width of the tire in millimeters, measured from sidewall to sidewall.
65: the sidewall height
The second number is the aspect ratio. It is the height of the sidewall as a percentage of the width. A 65 sidewall is 65% as tall as the tire is wide. Lower numbers mean a shorter sidewall.
R17: the wheel size
R means radial construction, which is nearly every tire today. The number after it is the diameter of the wheel in inches. A 17 only fits a 17-inch wheel.
The letters in front
P means passenger. LT means light truck: a stronger tire for heavier loads and towing. ST means special trailer and is for trailers only. If there is no letter, it is a metric passenger size.
102H: load and speed
The number at the end is the load index, which is how much weight each tire can carry. The letter is the speed rating. Choose a tire with a load index and speed rating at least as high as the one on your door sticker.