225/55R18 Tire Size in Inches and Millimeters

225/55R18 tires have a diameter of 27.8" (705 mm), a tread width of 8.9" (225 mm), and a wheel diameter of 18" (457.2 mm).The sidewall of the tire is 4.9" (124 mm), and the tire's circumference is 87.3" (2213.7 mm). This means a 225/55R18 tire will make make 726 revolutions per mile, or 452 revolutions per kilometer.

225/55R18 Tire Front
8.9"
27.8"
225/55R18 Tire Side
Tire Circumference
87.3"
18"
4.9"
726 Revs/Mile
SpecInchesMetric
Diameter27.8"705 mm
Width8.9"225 mm
Wheel18"457.2 mm
Sidewall4.9"124 mm
Circum87.3"2213.7 mm
Revolutions726 per mile452 per km

What Does 225/55R18 Mean?

The tire size 225/55R18 is a common size used on many trucks, SUVs, and other larger vehicles.

Here is what each part of the size designation represents:

  • 225: This number represents the width of the tire in millimeters. In this case, the tire is 225 millimeters wide.
  • 55: 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 55% 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.

225/55R18 tire size meaning

How To Convert 225/55R18 Into Inches

The 225/55R18 conversion is fairly simple. The first number in the tire size, 225, represents the width of the tire in millimeters. To convert this to inches, we divide 225 by 25.4 (since there are 25.4 millimeters in an inch). This gives us approximately 8.9 inches.

The second number in the tire size, 55, represents the aspect ratio or the height of the tire as a percentage of its width. To calculate the height in inches, we multiply 8.9 by 0.55, which gives us approximately 4.9 inches.

Finally, the last number in the tire size, 18, represents the diameter of the wheel rim in inches. Therefore, the tire size 225/55R18 can be expressed in inches as roughly 8.9 inches wide, 4.9 inches tall, and designed to fit a 18-inch wheel rim.

Frequently Asked Questions About 225/55R18 Tires

How tall is a 225/55R18 tire?

A 225/55R18 tire has an approximate height, also known as the overall diameter, of 27.8 inches (705 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 225/55R18 tire?

A 225/55R18 tire has a width of approximately 8.9 inches (225 millimeters). The width of the tire is the first number in the tire size designation, which in this case is “225”. 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 225/55R18 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
145/65R2027.4"696 mm20 mm
145/80R1827.1"689 mm18 mm
145/80R1928.1"715 mm19 mm
145/85R1827.7"703 mm18 mm
145/90R1727.3"694 mm17 mm
155/60R2027.3"694 mm20 mm
155/65R2028"710 mm20 mm
155/70R1927.6"701 mm19 mm
155/80R1827.8"705 mm18 mm
155/85R1828.4"721 mm18 mm
155/90R1627"686 mm16 mm
155/90R1728"712 mm17 mm
165/60R2027.8"706 mm20 mm
165/70R1827.1"689 mm18 mm
165/80R1727.4"696 mm17 mm
175/55R2027.6"700 mm20 mm
175/60R1927.3"693 mm19 mm
175/80R1627"686 mm16 mm
185/75R1626.9"684 mm16 mm
195/50R2027.7"704 mm20 mm
195/75R1627.5"698 mm16 mm
195/80R1527.3"693 mm15 mm
195/80R1628.3"718 mm16 mm
205/60R1827.7"703 mm18 mm
205/65R1727.5"698 mm17 mm
205/70R1627.3"694 mm16 mm
205/75R1527.1"689 mm15 mm
205/75R1628.1"714 mm16 mm
215/45R2027.6"702 mm20 mm
215/55R1827.3"693 mm18 mm
215/60R1727.2"690 mm17 mm
215/65R1627"686 mm16 mm
215/65R1728"712 mm17 mm
215/70R1627.9"708 mm16 mm
215/75R1527.7"703 mm15 mm
215/80R1528.5"725 mm15 mm
225/30R2227.4"695 mm22 mm
225/40R2027.1"688 mm20 mm
225/45R1927"685 mm19 mm
225/45R2028"710 mm20 mm
225/55R1827.8"705 mm18 mm
225/60R1727.6"702 mm17 mm
225/65R1627.5"698 mm16 mm
225/65R1728.5"724 mm17 mm
225/70R1527.4"697 mm15 mm
225/70R1628.4"722 mm16 mm
225/75R1427.3"694 mm14 mm
225/75R1528.3"719 mm15 mm
235/30R2227.6"701 mm22 mm
235/35R2127.4"697 mm21 mm
235/40R2027.4"696 mm20 mm
235/45R1927.4"695 mm19 mm
235/45R2028.3"720 mm20 mm
235/50R1827.3"693 mm18 mm
235/50R1928.3"719 mm19 mm
235/55R1727.2"690 mm17 mm
235/55R1828.1"715 mm18 mm
235/60R1627.1"688 mm16 mm
235/60R1728.1"714 mm17 mm
235/65R1527"687 mm15 mm
235/65R1628"712 mm16 mm
235/70R1427"686 mm14 mm
235/70R1528"711 mm15 mm
245/30R2227.8"707 mm22 mm
245/35R2127.8"705 mm21 mm
245/40R2027.7"704 mm20 mm
245/45R1927.7"703 mm19 mm
245/50R1827.7"703 mm18 mm
245/55R1727.6"702 mm17 mm
245/60R1627.6"700 mm16 mm
245/60R1728.6"726 mm17 mm
245/65R1527.5"699 mm15 mm
245/70R1427.6"700 mm14 mm
245/70R1528.5"725 mm15 mm
255/30R2127"687 mm21 mm
255/30R2228.1"713 mm22 mm
255/35R2027"686 mm20 mm
255/35R2128"711 mm21 mm
255/40R1927"687 mm19 mm
255/40R2028"712 mm20 mm
255/45R1827"687 mm18 mm
255/45R1928.1"713 mm19 mm
255/50R1727.1"688 mm17 mm
255/50R1828.1"713 mm18 mm
255/55R1627"686 mm16 mm
255/55R1728"712 mm17 mm
255/60R1527"687 mm15 mm
255/60R1628"712 mm16 mm
255/65R1528.1"713 mm15 mm
265/25R2227.2"691 mm22 mm
265/25R2328.2"716 mm23 mm
265/30R2127.3"693 mm21 mm
265/30R2228.3"719 mm22 mm
265/35R2027.3"694 mm20 mm
265/35R2128.3"719 mm21 mm
265/40R1927.4"695 mm19 mm
265/40R2028.3"720 mm20 mm
265/45R1827.4"695 mm18 mm
265/45R1928.4"721 mm19 mm
265/50R1828.5"723 mm18 mm
265/55R1728.5"724 mm17 mm
265/60R1527.5"699 mm15 mm
265/60R1628.5"724 mm16 mm
275/25R2227.4"697 mm22 mm
275/30R2127.5"699 mm21 mm
275/30R2228.5"725 mm22 mm
275/35R2027.6"700 mm20 mm
275/35R2128.5"725 mm21 mm
275/40R1927.7"703 mm19 mm
275/45R1827.8"705 mm18 mm
275/50R1727.9"708 mm17 mm
275/55R1627.9"708 mm16 mm
275/60R1427"686 mm14 mm
275/60R1528"711 mm15 mm
285/25R2227.6"701 mm22 mm
285/30R2127.8"705 mm21 mm
285/35R2027.9"708 mm20 mm
285/40R1827"685 mm18 mm
285/40R1928"711 mm19 mm
285/45R1828.1"713 mm18 mm
295/25R2227.8"707 mm22 mm
295/30R2027"686 mm20 mm
295/30R2128"711 mm21 mm
295/35R1927.1"689 mm19 mm
295/35R2028.1"714 mm20 mm
295/40R1827.3"693 mm18 mm
295/40R1928.3"719 mm19 mm
295/45R1727.5"698 mm17 mm
295/45R1828.5"723 mm18 mm
295/50R1627.6"702 mm16 mm
295/55R1527.8"705 mm15 mm
305/25R2127"685 mm21 mm
305/25R2228"711 mm22 mm
305/30R2027.2"692 mm20 mm
305/30R2128.2"717 mm21 mm
305/35R1927.4"697 mm19 mm
305/35R2028.4"722 mm20 mm
305/40R1827.6"701 mm18 mm
305/45R1727.8"706 mm17 mm
305/50R1527"687 mm15 mm
315/25R2228.2"717 mm22 mm
315/30R2027.5"698 mm20 mm
315/30R2128.5"723 mm21 mm
315/35R1927.7"703 mm19 mm
315/40R1827.9"709 mm18 mm
315/45R1627.2"690 mm16 mm
315/45R1728.2"716 mm17 mm
325/25R2127.4"695 mm21 mm
325/30R2027.7"704 mm20 mm
325/35R1827"685 mm18 mm
325/50R1527.8"707 mm15 mm
335/30R1927"685 mm19 mm
335/30R2028"710 mm20 mm
345/30R1927.2"691 mm19 mm
345/30R2028.2"716 mm20 mm
345/35R1827.5"699 mm18 mm
345/35R1928.5"725 mm19 mm
345/40R1727.9"708 mm17 mm
355/25R2128"711 mm21 mm
355/30R1927.4"697 mm19 mm
355/40R1627.2"690 mm16 mm