You call around, looking for a price on tires, or maybe even brakes. The attendant on the phone asks you for your tire size. You have no idea. All you know about your tires is they are black and round, and rotate when you press the gas. Where do you even find that information?
Here's a straightforward way to find your tire size from the sidewall of your tire:
Look for a number structure like this example: P215/60R16. It will run along the outside face of the sidewall. It may be at the bottom of the tire, so you might need to read it upside down.
The prefix "P" indicates the tire’s service type. P is a passenger rated tire. Other common types are LT for light truck use, T for temporary use as in spare tires, and ST for special trailer use only.
The first number, 215, is the width of the tire tread measured in millimeters.
The number after the slash, 60, is the profile of the tire. The profile is the height of the tire from the ground to the rim measured as a percentage. In this example, the height of the tire is 60 percent of the width of the tire.
The letter that comes next, R, indicates the type of tire construction. R is a radial tire. Another option, although less common, is ZR which indicates the tire is rated for high speed.
The last number in the sequence, 16, indicates the rim size for the tire measured in inches.
Historically, there have been other tire constructions used that are no longer commonplace. D indicated diagonal construction, or bias ply, and B was for belted tires. Both constructions are extremely uncommon to see on modern tires.
This article originally appeared on YourMechanic.com as How to Read Tire Size From a Sidewall and was authored by Jason Unrau.