285/40R18 Tire Size in Inches and Millimeters

285/40R18 tires have a diameter of 27" (685 mm), a tread width of 11.2" (285 mm), and a wheel diameter of 18" (457.2 mm).The sidewall of the tire is 4.5" (114 mm), and the tire's circumference is 84.8" (2150.9 mm). This means a 285/40R18 tire will make make 747 revolutions per mile, or 465 revolutions per kilometer.

285/40R18 Tire Front
285/40R18 Tire Side
Tire Circumference
747 Revs/Mile
Diameter27"685 mm
Width11.2"285 mm
Wheel18"457.2 mm
Sidewall4.5"114 mm
Circum84.8"2150.9 mm
Revolutions747 per mile465 per km

What Does 285/40R18 Mean?

The tire size 285/40R18 is a common size used on many trucks, SUVs, and other larger vehicles.

Here is what each part of the size designation represents:

  • 285: This number represents the width of the tire in millimeters. In this case, the tire is 285 millimeters wide.
  • 40: 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 40% 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.

285/40R18 tire size meaning

How To Convert 285/40R18 Into Inches

The 285/40R18 conversion is fairly simple. The first number in the tire size, 285, represents the width of the tire in millimeters. To convert this to inches, we divide 285 by 25.4 (since there are 25.4 millimeters in an inch). This gives us approximately 11.2 inches.

The second number in the tire size, 40, represents the aspect ratio or the height of the tire as a percentage of its width. To calculate the height in inches, we multiply 11.2 by 0.40, which gives us approximately 4.5 inches.

Finally, the last number in the tire size, 18, represents the diameter of the wheel rim in inches. Therefore, the tire size 285/40R18 can be expressed in inches as roughly 11.2 inches wide, 4.5 inches tall, and designed to fit a 18-inch wheel rim.

Nitto NT555 G2 all_ Season Radial Tire-285/40ZR18 105W
Nitto NT555 G2 all_ Season Radial Tire-285/40ZR18 105W
Circumferential grooves channel water out of contact patch for better traction; Reinforced shoulder treads improve durability and cornering grip
Hankook Ventus V12 evo 2 Summer Radial Tire - 275/40R18 Y
Hankook Ventus V12 evo 2 Summer Radial Tire - 275/40R18 Y
Style : black_sidewall; The Package Length of the Product is 26.7 inches; The Package Width of the Product is 26.7 inches
Michelin Pilot Sport All Season 4 Performance Tire 275/40ZR18/XL 103Y
Michelin Pilot Sport All Season 4 Performance Tire 275/40ZR18/XL 103Y
Performance made to last.; Elevate your potential in all seasons.; The first all season tire chosen by Chevrolet for the Corvette.
Toyo Tires EXTENSA HPII All-Season Radial Tire - 275/40R18 99W
Toyo Tires EXTENSA HPII All-Season Radial Tire - 275/40R18 99W
Fit type: Universal Fit; Load capacity: 1709.0 pounds; Speed rating: W

Frequently Asked Questions About 285/40R18 Tires

How tall is a 285/40R18 tire?

A 285/40R18 tire has an approximate height, also known as the overall diameter, of 27 inches (685 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 285/40R18 tire?

A 285/40R18 tire has a width of approximately 11.2 inches (285 millimeters). The width of the tire is the first number in the tire size designation, which in this case is “285”. 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 285/40R18 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.

135/70R1926.5"673 mm19 mm
135/80R1826.5"673 mm18 mm
135/90R1726.6"676 mm17 mm
145/60R2026.9"682 mm20 mm
145/65R2027.4"696 mm20 mm
145/80R1827.1"689 mm18 mm
145/85R1827.7"703 mm18 mm
145/90R1626.3"668 mm16 mm
145/90R1727.3"694 mm17 mm
155/60R2027.3"694 mm20 mm
155/70R1826.6"675 mm18 mm
155/70R1927.6"701 mm19 mm
155/80R1726.8"680 mm17 mm
155/80R1827.8"705 mm18 mm
155/90R1627"686 mm16 mm
165/70R1827.1"689 mm18 mm
165/80R1626.4"670 mm16 mm
165/80R1727.4"696 mm17 mm
175/55R2027.6"700 mm20 mm
175/60R1927.3"693 mm19 mm
175/75R1626.3"668 mm16 mm
175/80R1627"686 mm16 mm
185/75R1626.9"684 mm16 mm
185/80R1526.7"677 mm15 mm
195/50R2027.7"704 mm20 mm
195/75R1526.5"673 mm15 mm
195/75R1627.5"698 mm16 mm
195/80R1426.3"668 mm14 mm
195/80R1527.3"693 mm15 mm
205/55R1826.9"683 mm18 mm
205/60R1726.7"678 mm17 mm
205/60R1827.7"703 mm18 mm
205/65R1626.5"672 mm16 mm
205/65R1727.5"698 mm17 mm
205/70R1526.3"669 mm15 mm
205/70R1627.3"694 mm16 mm
205/75R1527.1"689 mm15 mm
215/45R2027.6"702 mm20 mm
215/50R1826.5"673 mm18 mm
215/55R1726.3"668 mm17 mm
215/55R1827.3"693 mm18 mm
215/60R1727.2"690 mm17 mm
215/65R1627"686 mm16 mm
215/70R1526.9"683 mm15 mm
215/75R1426.7"678 mm14 mm
215/75R1527.7"703 mm15 mm
225/30R2227.4"695 mm22 mm
225/35R2026.2"666 mm20 mm
225/40R2027.1"688 mm20 mm
225/45R1927"685 mm19 mm
225/50R1826.9"683 mm18 mm
225/55R1726.8"680 mm17 mm
225/55R1827.8"705 mm18 mm
225/60R1626.6"676 mm16 mm
225/60R1727.6"702 mm17 mm
225/65R1526.5"673 mm15 mm
225/65R1627.5"698 mm16 mm
225/70R1426.5"672 mm14 mm
225/70R1527.4"697 mm15 mm
225/75R1427.3"694 mm14 mm
235/30R2126.6"675 mm21 mm
235/30R2227.6"701 mm22 mm
235/35R2026.5"672 mm20 mm
235/35R2127.4"697 mm21 mm
235/40R1926.4"671 mm19 mm
235/40R2027.4"696 mm20 mm
235/45R1826.3"669 mm18 mm
235/45R1927.4"695 mm19 mm
235/50R1726.3"668 mm17 mm
235/50R1827.3"693 mm18 mm
235/55R1727.2"690 mm17 mm
235/60R1627.1"688 mm16 mm
235/65R1527"687 mm15 mm
235/70R1427"686 mm14 mm
240/55R1626.4"670 mm16 mm
245/30R2126.8"681 mm21 mm
245/35R2026.8"680 mm20 mm
245/35R2127.8"705 mm21 mm
245/40R1926.7"679 mm19 mm
245/40R2027.7"704 mm20 mm
245/45R1826.7"677 mm18 mm
245/45R1927.7"703 mm19 mm
245/50R1726.7"678 mm17 mm
245/50R1827.7"703 mm18 mm
245/55R1626.6"676 mm16 mm
245/55R1727.6"702 mm17 mm
245/60R1526.6"675 mm15 mm
245/60R1627.6"700 mm16 mm
245/65R1527.5"699 mm15 mm
245/70R1427.6"700 mm14 mm
255/30R2127"687 mm21 mm
255/35R2027"686 mm20 mm
255/40R1927"687 mm19 mm
255/45R1827"687 mm18 mm
255/50R1727.1"688 mm17 mm
255/55R1627"686 mm16 mm
255/60R1527"687 mm15 mm
265/25R2227.2"691 mm22 mm
265/30R2026.3"668 mm20 mm
265/30R2127.3"693 mm21 mm
265/35R1926.3"669 mm19 mm
265/35R2027.3"694 mm20 mm
265/40R1826.3"669 mm18 mm
265/40R1927.4"695 mm19 mm
265/45R1827.4"695 mm18 mm
265/50R1626.5"672 mm16 mm
265/60R1426.5"674 mm14 mm
265/60R1527.5"699 mm15 mm
275/25R2126.4"671 mm21 mm
275/25R2227.4"697 mm22 mm
275/30R2026.5"674 mm20 mm
275/30R2127.5"699 mm21 mm
275/35R1926.6"675 mm19 mm
275/35R2027.6"700 mm20 mm
275/40R1826.7"677 mm18 mm
275/40R1927.7"703 mm19 mm
275/45R1827.8"705 mm18 mm
275/50R1626.9"682 mm16 mm
275/55R1526.9"683 mm15 mm
275/60R1427"686 mm14 mm
285/25R2227.6"701 mm22 mm
285/30R2026.8"680 mm20 mm
285/30R2127.8"705 mm21 mm
285/35R1926.9"683 mm19 mm
285/40R1827"685 mm18 mm
285/50R1526.3"667 mm15 mm
295/25R2126.8"681 mm21 mm
295/30R2027"686 mm20 mm
295/35R1927.1"689 mm19 mm
295/40R1726.3"668 mm17 mm
295/40R1827.3"693 mm18 mm
295/45R1727.5"698 mm17 mm
295/50R1526.7"677 mm15 mm
295/50R1627.6"702 mm16 mm
295/55R1527.8"705 mm15 mm
305/25R2127"685 mm21 mm
305/30R1926.3"667 mm19 mm
305/30R2027.2"692 mm20 mm
305/35R1826.4"671 mm18 mm
305/35R1927.4"697 mm19 mm
305/40R1827.6"701 mm18 mm
305/50R1527"687 mm15 mm
315/25R2026.2"666 mm20 mm
315/30R1926.5"673 mm19 mm
315/30R2027.5"698 mm20 mm
315/35R1826.7"677 mm18 mm
315/35R1927.7"703 mm19 mm
315/45R1627.2"690 mm16 mm
325/25R2026.4"670 mm20 mm
325/25R2127.4"695 mm21 mm
325/30R1926.7"679 mm19 mm
325/30R2027.7"704 mm20 mm
325/35R1827"685 mm18 mm
335/25R2026.6"676 mm20 mm
335/30R1927"685 mm19 mm
335/35R1726.2"666 mm17 mm
345/25R2026.8"680 mm20 mm
345/30R1826.2"665 mm18 mm
345/30R1927.2"691 mm19 mm
345/35R1827.5"699 mm18 mm
355/30R1927.4"697 mm19 mm
355/40R1627.2"690 mm16 mm
375/20R2126.9"683 mm21 mm