315/30R18 Tire Size in Inches and Millimeters

315/30R18 tires have a diameter of 25.5" (647 mm), a tread width of 12.4" (315 mm), and a wheel diameter of 18" (457.2 mm).The sidewall of the tire is 3.7" (95 mm), and the tire's circumference is 80.1" (2031.6 mm). This means a 315/30R18 tire will make make 791 revolutions per mile, or 492 revolutions per kilometer.

315/30R18 Tire Front
315/30R18 Tire Side
Tire Circumference
791 Revs/Mile
Diameter25.5"647 mm
Width12.4"315 mm
Wheel18"457.2 mm
Sidewall3.7"95 mm
Circum80.1"2031.6 mm
Revolutions791 per mile492 per km

What Does 315/30R18 Mean?

The tire size 315/30R18 is a common size used on many trucks, SUVs, and other larger vehicles.

Here is what each part of the size designation represents:

  • 315: This number represents the width of the tire in millimeters. In this case, the tire is 315 millimeters wide.
  • 30: 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 30% 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.

315/30R18 tire size meaning

How To Convert 315/30R18 Into Inches

The 315/30R18 conversion is fairly simple. The first number in the tire size, 315, represents the width of the tire in millimeters. To convert this to inches, we divide 315 by 25.4 (since there are 25.4 millimeters in an inch). This gives us approximately 12.4 inches.

The second number in the tire size, 30, represents the aspect ratio or the height of the tire as a percentage of its width. To calculate the height in inches, we multiply 12.4 by 0.30, which gives us approximately 3.7 inches.

Finally, the last number in the tire size, 18, represents the diameter of the wheel rim in inches. Therefore, the tire size 315/30R18 can be expressed in inches as roughly 12.4 inches wide, 3.7 inches tall, and designed to fit a 18-inch wheel rim.

Nitto NT01 High Performance Tire - 315/30R18 98Z
Nitto NT01 High Performance Tire - 315/30R18 98Z
High-performance summer tires for sporty coupes and sedans; Supreme dry performance; Optimized sidewall construction for exceptional response
Nitto NT01 all_ Season Radial Tire-315/30R18 98W
Nitto NT01 all_ Season Radial Tire-315/30R18 98W
package dimensions :26.0 " L x 26.0 " W x 13.0 " H; Product type :VEHICLE TIRE; country of origin:Japan
YOKOHAMA 315/30R18 98Y ADVAN A052 BW
YOKOHAMA 315/30R18 98Y ADVAN A052 BW
315/30R18 98Y YOKOHAMA ADVAN A052 BW

Frequently Asked Questions About 315/30R18 Tires

How tall is a 315/30R18 tire?

A 315/30R18 tire has an approximate height, also known as the overall diameter, of 25.5 inches (647 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 315/30R18 tire?

A 315/30R18 tire has a width of approximately 12.4 inches (315 millimeters). The width of the tire is the first number in the tire size designation, which in this case is “315”. 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 315/30R18 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.

115/70R1925.4"645 mm19 mm
115/95R1725.6"650 mm17 mm
125/70R1824.9"633 mm18 mm
125/70R1925.9"659 mm19 mm
125/80R1724.9"632 mm17 mm
125/90R1624.9"632 mm16 mm
135/60R1925.4"645 mm19 mm
135/70R1825.5"647 mm18 mm
135/80R1725.5"648 mm17 mm
135/90R1625.6"650 mm16 mm
145/65R1825.4"645 mm18 mm
145/70R1725"636 mm17 mm
145/70R1826"661 mm18 mm
145/80R1625.1"638 mm16 mm
145/80R1726.1"664 mm17 mm
155/60R1825.3"643 mm18 mm
155/70R1725.6"650 mm17 mm
155/80R1524.8"629 mm15 mm
155/80R1625.7"654 mm16 mm
165/70R1726.1"664 mm17 mm
165/80R1525.4"645 mm15 mm
175/75R1525.3"643 mm15 mm
175/80R1425"636 mm14 mm
185/55R1826"661 mm18 mm
185/60R1624.7"628 mm16 mm
185/60R1725.7"654 mm17 mm
185/65R1625.4"646 mm16 mm
185/70R1525.2"641 mm15 mm
185/75R1425"634 mm14 mm
185/80R1425.7"652 mm14 mm
195/50R1724.7"628 mm17 mm
195/55R1725.4"646 mm17 mm
195/60R1625.2"640 mm16 mm
195/65R1525"635 mm15 mm
195/65R1626"660 mm16 mm
195/70R1424.8"630 mm14 mm
195/70R1525.8"655 mm15 mm
195/75R1425.5"648 mm14 mm
205/45R1825.2"641 mm18 mm
205/50R1725.1"638 mm17 mm
205/50R1826.1"663 mm18 mm
205/55R1624.9"632 mm16 mm
205/55R1725.9"658 mm17 mm
205/60R1625.7"652 mm16 mm
205/65R1525.5"647 mm15 mm
205/70R1425.4"644 mm14 mm
205/75R1426.1"664 mm14 mm
215/30R2025.1"638 mm20 mm
215/35R1924.9"633 mm19 mm
215/40R1824.8"629 mm18 mm
215/40R1925.8"655 mm19 mm
215/45R1825.6"651 mm18 mm
215/50R1725.5"648 mm17 mm
215/55R1625.3"642 mm16 mm
215/60R1525.2"639 mm15 mm
215/60R1626.1"664 mm16 mm
215/65R1425"636 mm14 mm
215/65R1526"661 mm15 mm
215/70R1425.9"658 mm14 mm
225/30R2025.4"644 mm20 mm
225/35R1925.2"641 mm19 mm
225/35R2026.2"666 mm20 mm
225/40R1825.1"637 mm18 mm
225/40R1926.1"663 mm19 mm
225/45R1725"634 mm17 mm
225/45R1825.9"659 mm18 mm
225/50R1624.9"632 mm16 mm
225/50R1725.9"658 mm17 mm
225/55R1524.8"629 mm15 mm
225/55R1625.7"654 mm16 mm
225/60R1525.6"651 mm15 mm
235/30R2025.6"650 mm20 mm
235/35R1925.5"647 mm19 mm
235/40R1825.4"645 mm18 mm
235/45R1725.4"644 mm17 mm
235/50R1625.3"642 mm16 mm
235/55R1525.2"639 mm15 mm
235/55R1626.1"664 mm16 mm
235/60R1425.1"638 mm14 mm
235/60R1526.1"663 mm15 mm
245/30R1924.8"631 mm19 mm
245/30R2025.8"656 mm20 mm
245/35R1824.8"629 mm18 mm
245/35R1925.8"655 mm19 mm
245/40R1724.7"628 mm17 mm
245/40R1825.7"653 mm18 mm
245/45R1725.7"652 mm17 mm
245/50R1625.7"652 mm16 mm
245/60R1425.6"650 mm14 mm
255/30R1925.1"637 mm19 mm
255/30R2026.1"662 mm20 mm
255/35R1825"635 mm18 mm
255/35R1926"661 mm19 mm
255/40R1725"636 mm17 mm
255/40R1826"661 mm18 mm
255/45R1726.1"662 mm17 mm
255/50R1626.1"662 mm16 mm
255/55R1425"636 mm14 mm
255/55R1526"661 mm15 mm
255/60R1426.1"662 mm14 mm
265/30R1925.3"643 mm19 mm
265/35R1825.3"643 mm18 mm
265/40R1725.4"644 mm17 mm
265/45R1625.4"644 mm16 mm
265/50R1525.5"647 mm15 mm
275/25R2025.4"646 mm20 mm
275/30R1925.6"649 mm19 mm
275/35R1825.6"649 mm18 mm
275/40R1725.7"652 mm17 mm
275/45R1625.7"654 mm16 mm
275/50R1525.9"657 mm15 mm
285/25R2025.6"650 mm20 mm
285/30R1824.8"629 mm18 mm
285/30R1925.8"655 mm19 mm
285/35R1724.9"632 mm17 mm
285/35R1825.9"657 mm18 mm
285/40R1726"660 mm17 mm
295/25R1924.8"631 mm19 mm
295/25R2025.8"656 mm20 mm
295/30R1825"635 mm18 mm
295/30R1926"661 mm19 mm
295/35R1725.1"638 mm17 mm
295/35R1826.1"663 mm18 mm
305/25R1925"635 mm19 mm
305/25R2026"660 mm20 mm
305/30R1825.2"641 mm18 mm
305/35R1725.4"646 mm17 mm
315/25R1925.2"641 mm19 mm
315/25R2026.2"666 mm20 mm
315/30R1825.5"647 mm18 mm
315/35R1725.7"652 mm17 mm
315/40R1625.9"658 mm16 mm
335/25R1925.6"651 mm19 mm
335/30R1825.9"659 mm18 mm
335/35R1726.2"666 mm17 mm
345/30R1826.2"665 mm18 mm
355/25R1926"661 mm19 mm