What Do the Numbers on a Tire's Size Mean? People often ask, "What do the numbers in a tire's size mean?" A friend of mine recently placed the following post on her Facebook wall: "Need some automotive help here. Will P225/60R16 tires fit a car that right now is 'wearing' LT215/70R16 tires?" The answers she got were as varied as could be. Is the width of the tire measured in millimeters from sidewall to sidewall. The first three-digit number in the tire size refers to the tire width. For instance, in a size P215/65 R15 tire, the width is 215 millimeters. Aspect Ratio Is the ratio of the height of the tire's cross-section to its width. Tire Size Meaning There are two ways that tire manufacturers display tire size, inches and metric. To find the tire size meaning in inches is very straight forward. Example A : 33X12.50R15 The first number is your overall diameter of the tire. In this example the tire diameter or "height" is 33 inches tall. The most basic information that you'll find on a tire's sidewall is related to its size. This is normally written as 185/65R15, for example, though you'll sometimes see "P" (for passenger cars) Tyre size explained Tyre dimensions. Width: The section width of your tyre in millimetres, from the inner sidewall to the outer sidewall. Example: 195mm. Aspect Ratio: The height of your tyre from the base of the tread to the rim, as a percentage of the tread width. Low profile tyres have smaller aspect ratios. Tire size can be defined as a collection of numbers and letters that describe tire type, width, sidewall height, and wheel diameter — alongside other information. An example of a common tire size is as follows: P225/65R17. The tire size for your vehicle and wheels can be found in two places: The sidewall of your tire. Diameter : 35 The Diameter of this tire size is 35 inches. The first number in a high flotation tire size is the overall diameter of the tire. Section Width : 12.50 The width of this tire size is 12.5 inches. The second number in a high flotation tire size is the width of the tire in inches. Tire Construction : R A tire's aspect ratio is its height to width in percentage. A tire with 205 mm width and 55 mm sidewall height has a 55% aspect ratio. Aspect ratio impacts tire diameter. The first number in a tire size is the width in millimeters, and the second represents the aspect ratio. The number 185 is the tire's width in millimeters, from one sidewall to the other. The number 60 after the forward slash character means the tire's height from rim to tread is 60 percent of its width, which again is 185 millimeters. R14 means the tire is meant to fit on a 14-in. diameter wheel. P denotes passenger-car tire. Some may start with an LT prefix, used on heavy-duty trucks. The number 235 is the cross-section width in millimeters, and 65 is the ratio of sidewall height to 2HR1.