165/40R18 in inches

165/40R18 — what does it mean?

• 165 stands for tread width in millimeters
• 40 is an aspect ration between the tread width and the sidewall in percents
• R means that the tire has a radial construction
• 18 is a wheel diameter (or rim) in inches

How to convert 165 40R18 to inches?

First of all, we need to divide 165 mm (width) by 25.4 (mm to inch conversion), which will give us a width of 6.5″. Then, 40% of the 6.5″ will result in 2.6″ sidewall.

To get the total height or tire diameter, we need to sum the 18″ rim diameter with two of the sidewall heights. It will result in a 23.2″ total tire diameter (or height).

For your convenience, below is a table for 165/40R18 conversion to inches:

Alternatives to a 165/40R18 tire

If you're looking to upsize your 165 40R18 tires, try to stay within 3% deviation of an overall diameter for safety reasons.