How to Get a Tire Size in Inches
- 1). Calculate the sidewall height. If the sidewall data reads "225/45R16," then you know the width is 225 mm, and the sidewall height is 45 percent of that. Therefore, multiply the width by the decimal format of 45 percent. The decimal format of a percentage is obtained by dividing the percentage by 100; thus, the decimal format of the example is 0.45. Multiplying 225 mm by 0.45, tells you the sidewall height is 101 mm (rounded).
- 2). Convert the sidewall height into inches. Since there are 25.4 mm in an inch, you divide the number of millimeters by 25.4. Therefore, the sidewall height in inches would be 101 mm divided by 25.4 mm/in, which equals 4.0 inches (rounded).
- 3). Multiply the sidewall height by two, since there is a sidewall above and below the rim. If you scanned up from the ground, you would see a sidewall, a rim and then another sidewall. In the example, 4-inch sidewall multiplied by 2 sidewalls equals 8 inches of sidewall.
- 4). Add the rim diameter to the total sidewall height. The rim diameter is the last number in the series, 16 in the example. Therefore, the total tire diameter would be 16 inches plus 8 inches, which equals 24 inches in diameter.
