305/75R18 Tire Size in Inches and Millimeters

305/75R18 tires have a diameter of 36" (915 mm), a tread width of 12" (305 mm), and a wheel diameter of 18" (457.2 mm).The sidewall of the tire is 9" (229 mm), and the tire's circumference is 113" (2873.1 mm). This means a 305/75R18 tire will make make 561 revolutions per mile, or 348 revolutions per kilometer.

305/75R18 Tire Front
12"
36"
305/75R18 Tire Side
Tire Circumference
113"
18"
9"
561 Revs/Mile
SpecInchesMetric
Diameter36"915 mm
Width12"305 mm
Wheel18"457.2 mm
Sidewall9"229 mm
Circum113"2873.1 mm
Revolutions561 per mile348 per km

What Does 305/75R18 Mean?

The tire size 305/75R18 is a common size used on many trucks, SUVs, and other larger vehicles.

Here is what each part of the size designation represents:

  • 305: This number represents the width of the tire in millimeters. In this case, the tire is 305 millimeters wide.
  • 75: This number represents the aspect ratio of the tire, which is the height of the tire's sidewall as a percentage of its width. In this case, the sidewall height is 75% of the tire's width.
  • R: This letter indicates the tire's construction type. “R” stands for radial construction, which is the most common type of tire construction today.
  • 18: This number represents the diameter of the wheel that the tire is designed to fit on, in inches. In this case, the tire is designed to fit on a 18-inch wheel.

305/75R18 tire size meaning

How To Convert 305/75R18 Into Inches

The 305/75R18 conversion is fairly simple. The first number in the tire size, 305, represents the width of the tire in millimeters. To convert this to inches, we divide 305 by 25.4 (since there are 25.4 millimeters in an inch). This gives us approximately 12 inches.

The second number in the tire size, 75, represents the aspect ratio or the height of the tire as a percentage of its width. To calculate the height in inches, we multiply 12 by 0.75, which gives us approximately 9 inches.

Finally, the last number in the tire size, 18, represents the diameter of the wheel rim in inches. Therefore, the tire size 305/75R18 can be expressed in inches as roughly 12 inches wide, 9 inches tall, and designed to fit a 18-inch wheel rim.

Frequently Asked Questions About 305/75R18 Tires

How tall is a 305/75R18 tire?

A 305/75R18 tire has an approximate height, also known as the overall diameter, of 36 inches (915 mm). This height can vary slightly depending on the brand and model of the tire, as well as the amount of air pressure in the tire.

How wide is a 305/75R18 tire?

A 305/75R18 tire has a width of approximately 12 inches (305 millimeters). The width of the tire is the first number in the tire size designation, which in this case is “305”. It’s important to note that the actual width of the tire may vary slightly depending on the brand and model of the tire, and the width may also be affected by the amount of air pressure in the tire.

Alternate 305/75R18 Replacement Tire Sizes

Upsizing your wheels or tires? Replacement tires must be within 3% of the diametor of the original tire. The following sizes fall within that range - click on any size to see detailed info about that tire and wheel combination.

SizeDiameterWidthWheel
255/30R3036.1"916 mm30 mm
275/25R3035.4"900 mm30 mm
275/80R1835.3"897 mm18 mm
295/65R2035.1"892 mm20 mm
305/55R2235.2"895 mm22 mm
305/75R1836"915 mm18 mm
315/20R3035"888 mm30 mm
315/40R2635.9"912 mm26 mm
315/45R2435.2"894 mm24 mm
315/50R2436.5"926 mm24 mm
315/70R1835.4"899 mm18 mm
325/35R2837"939 mm28 mm
325/45R2435.5"902 mm24 mm
325/55R2236.1"917 mm22 mm
325/60R2035.4"898 mm20 mm
325/70R1735"888 mm17 mm
325/80R1636.5"926 mm16 mm
335/35R2635.2"894 mm26 mm
335/55R2236.5"927 mm22 mm
345/45R2436.2"920 mm24 mm
345/75R1636.4"924 mm16 mm
355/40R2435.2"894 mm24 mm
355/60R2036.8"934 mm20 mm
355/65R1836.2"919 mm18 mm
355/70R1635.6"904 mm16 mm
355/70R1736.6"930 mm17 mm
365/70R1636.1"918 mm16 mm
375/40R2435.8"910 mm24 mm
375/45R2235.3"897 mm22 mm
375/55R2036.2"920 mm20 mm
375/60R1835.7"907 mm18 mm
375/65R1635.2"894 mm16 mm