305/40R18 in inches

How tall is a 305 40R18 tire?

When converted to inches, the equivalent of a 305/40R18 tire size is 27.6x12R18. It means that:

  • height overall (or diameter) is 27.6 inches
  • tread width is 12 inches
  • wheel diameter is 18 inches

Learn more

305/40R18 tire size in inches
305/40R18 tire size chart

305/40R18 tire size in inches

305/40R18 Height / overall diameter: 27.6 inches
Height / overall diameter
27.6 inches
305/40R18 Tread width: 12 inches
Tread width
12 inches
305/40R18 Sidewall: 4.8 inches
Sidewall
4.8 inches
305/40R18 Wheel diameter: 18 inches
Wheel diameter
18 inches
305/40R18 Circumference: 86.7 inches
Circumference
86.7 inches
305/40R18 Revolutions: 731 per mile
Revolutions
731 per mile

305/40R18 — what does it mean?

  • 305 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

305/40R18 tire code
305/40R18 tire code

How to convert 305 40R18 to inches?

First of all, we need to divide 305 mm (width) by 25.4 (mm to inch conversion), which will give us a width of 12″. Then, 40% of the 12″ will result in 4.8″ 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 27.6″ total tire diameter (or height).

For your convenience, below is a table for 305/40R18 conversion to inches:

Inches Metric
Overall diameter (height) 27.6″ 701 mm
Tread width 12″ 305 mm
Wheel diameter 18″ 701 mm
Sidewall height 4.8″ 122 mm
Circumference 86.7″ 2201 mm
Revolutions 731 / ml 454 / km

Alternatives to a 305/40R18 tire

If you're looking to upsize your 305 40R18 tires, try to stay within 3% deviation of an overall diameter for safety reasons.

Tire Tire diameter Width Wheel Size
145/80R18 27.2″ -0.36% 5.7″ 18″
145/85R18 27.6″ 0% 5.7″ 18″
155/80R18 27.8″ 0.18% 6.1″ 18″
155/85R18 28.4″ 0.7% 6.1″ 18″
165/70R18 27.2″ -0.36% 6.5″ 18″
205/55R18 26.8″ -0.72% 8.1″ 18″
205/60R18 27.6″ 0% 8.1″ 18″
215/55R18 27.2″ -0.36% 8.5″ 18″
225/50R18 26.8″ -0.72% 8.9″ 18″
225/55R18 27.8″ 0.18% 8.9″ 18″