With the P-Metric system, Section Width is measured in millimeters.

To convert millimeters into inches, divide by 25.4. The Aspect Ratio (Section Height divided by Section Width) helps provide more dimensional information about the tire size.

Example:

(1) P = Certain tire type used on light duty vehicles such as passenger cars
(2) Section Width in millimeters
(3) Aspect Ratio (= section height 7 section width).
(4) R = Radial Construction
(5) Rim diameter in inches