315/40R21 Tire Size in Inches and Millimeters
315/40R21 tires have a diameter of 30.9" (785 mm), a tread width of 12.4" (315 mm), and a wheel diameter of 21" (533.4 mm).The sidewall of the tire is 5" (126 mm), and the tire's circumference is 97" (2464.9 mm). This means a 315/40R21 tire will make make 653 revolutions per mile, or 406 revolutions per kilometer.
Spec | Inches | Metric |
---|---|---|
Diameter | 30.9" | 785 mm |
Width | 12.4" | 315 mm |
Wheel | 21" | 533.4 mm |
Sidewall | 5" | 126 mm |
Circum | 97" | 2464.9 mm |
Revolutions | 653 per mile | 406 per km |
What Does 315/40R21 Mean?
The tire size 315/40R21 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.
- 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.
- 21: 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 21-inch wheel.
How To Convert 315/40R21 Into Inches
The 315/40R21 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, 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 12.4 by 0.40, which gives us approximately 5 inches.
Finally, the last number in the tire size, 21, represents the diameter of the wheel rim in inches. Therefore, the tire size 315/40R21 can be expressed in inches as roughly 12.4 inches wide, 5 inches tall, and designed to fit a 21-inch wheel rim.
Frequently Asked Questions About 315/40R21 Tires
How tall is a 315/40R21 tire?
A 315/40R21 tire has an approximate height, also known as the overall diameter, of 30.9 inches (785 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 315/40R21 tire?
A 315/40R21 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 315/40R21 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.
Size | Diameter | Width | Wheel |
---|---|---|---|
165/90R19 | 30.7" | 781 mm | 19 mm |
175/80R19 | 30" | 763 mm | 19 mm |
175/90R18 | 30.4" | 773 mm | 18 mm |
215/85R16 | 30.4" | 772 mm | 16 mm |
225/75R17 | 30.3" | 770 mm | 17 mm |
225/75R18 | 31.3" | 795 mm | 18 mm |
225/85R16 | 31" | 788 mm | 16 mm |
235/55R20 | 30.2" | 766 mm | 20 mm |
235/60R19 | 30.1" | 765 mm | 19 mm |
235/65R18 | 30" | 763 mm | 18 mm |
235/65R19 | 31.1" | 789 mm | 19 mm |
235/70R17 | 30" | 762 mm | 17 mm |
235/70R18 | 31" | 787 mm | 18 mm |
235/75R17 | 30.9" | 784 mm | 17 mm |
235/80R16 | 30.8" | 782 mm | 16 mm |
235/80R17 | 31.8" | 808 mm | 17 mm |
235/85R16 | 31.7" | 806 mm | 16 mm |
245/60R20 | 31.6" | 802 mm | 20 mm |
245/65R18 | 30.5" | 775 mm | 18 mm |
245/70R17 | 30.6" | 776 mm | 17 mm |
245/70R18 | 31.5" | 801 mm | 18 mm |
245/75R16 | 30.5" | 774 mm | 16 mm |
245/75R17 | 31.5" | 800 mm | 17 mm |
255/30R24 | 30.1" | 764 mm | 24 mm |
255/40R22 | 30" | 763 mm | 22 mm |
255/45R21 | 30" | 763 mm | 21 mm |
255/45R22 | 31.1" | 789 mm | 22 mm |
255/50R20 | 30.1" | 764 mm | 20 mm |
255/50R21 | 31.1" | 789 mm | 21 mm |
255/55R19 | 30" | 763 mm | 19 mm |
255/55R20 | 31" | 788 mm | 20 mm |
255/60R18 | 30" | 763 mm | 18 mm |
255/60R19 | 31.1" | 789 mm | 19 mm |
255/65R17 | 30.1" | 764 mm | 17 mm |
255/65R18 | 31.1" | 789 mm | 18 mm |
255/70R16 | 30.1" | 764 mm | 16 mm |
255/70R17 | 31.1" | 790 mm | 17 mm |
255/75R15 | 30" | 763 mm | 15 mm |
265/40R22 | 30.4" | 771 mm | 22 mm |
265/45R21 | 30.4" | 771 mm | 21 mm |
265/45R22 | 31.4" | 797 mm | 22 mm |
265/50R20 | 30.5" | 774 mm | 20 mm |
265/55R19 | 30.5" | 775 mm | 19 mm |
265/60R18 | 30.5" | 775 mm | 18 mm |
265/65R17 | 30.6" | 776 mm | 17 mm |
265/65R18 | 31.5" | 801 mm | 18 mm |
265/70R16 | 30.6" | 778 mm | 16 mm |
265/70R17 | 31.7" | 804 mm | 17 mm |
265/75R15 | 30.7" | 779 mm | 15 mm |
265/75R16 | 31.7" | 804 mm | 16 mm |
275/25R26 | 31.4" | 798 mm | 26 mm |
275/30R24 | 30.6" | 776 mm | 24 mm |
275/40R22 | 30.7" | 779 mm | 22 mm |
275/40R23 | 31.7" | 804 mm | 23 mm |
275/45R21 | 30.7" | 781 mm | 21 mm |
275/45R22 | 31.8" | 807 mm | 22 mm |
275/50R20 | 30.9" | 784 mm | 20 mm |
275/55R19 | 30.9" | 785 mm | 19 mm |
275/60R17 | 30" | 762 mm | 17 mm |
275/60R18 | 31" | 787 mm | 18 mm |
275/65R16 | 30.1" | 764 mm | 16 mm |
275/65R17 | 31.1" | 790 mm | 17 mm |
275/70R15 | 30.2" | 767 mm | 15 mm |
275/70R16 | 31.2" | 792 mm | 16 mm |
285/30R24 | 30.8" | 782 mm | 24 mm |
285/35R23 | 30.9" | 784 mm | 23 mm |
285/40R22 | 31" | 787 mm | 22 mm |
285/45R20 | 30.1" | 764 mm | 20 mm |
285/45R21 | 31.1" | 789 mm | 21 mm |
285/50R20 | 31.3" | 794 mm | 20 mm |
285/55R18 | 30.4" | 771 mm | 18 mm |
285/55R19 | 31.4" | 797 mm | 19 mm |
285/60R17 | 30.5" | 774 mm | 17 mm |
285/60R18 | 31.5" | 799 mm | 18 mm |
285/65R16 | 30.6" | 776 mm | 16 mm |
285/65R17 | 31.6" | 802 mm | 17 mm |
285/70R15 | 30.7" | 781 mm | 15 mm |
285/70R16 | 31.7" | 806 mm | 16 mm |
295/25R26 | 31.8" | 808 mm | 26 mm |
295/30R23 | 30" | 762 mm | 23 mm |
295/30R24 | 31" | 788 mm | 24 mm |
295/35R22 | 30.1" | 765 mm | 22 mm |
295/35R23 | 31.1" | 790 mm | 23 mm |
295/40R21 | 30.3" | 769 mm | 21 mm |
295/40R22 | 31.3" | 795 mm | 22 mm |
295/45R20 | 30.5" | 774 mm | 20 mm |
295/50R20 | 31.7" | 804 mm | 20 mm |
295/65R15 | 30.1" | 765 mm | 15 mm |
295/65R16 | 31.1" | 790 mm | 16 mm |
305/35R22 | 30.4" | 773 mm | 22 mm |
305/35R23 | 31.4" | 798 mm | 23 mm |
305/40R22 | 31.6" | 803 mm | 22 mm |
305/45R20 | 30.8" | 782 mm | 20 mm |
305/60R17 | 31.4" | 798 mm | 17 mm |
315/30R24 | 31.5" | 800 mm | 24 mm |
315/35R22 | 30.7" | 779 mm | 22 mm |
315/40R21 | 30.9" | 785 mm | 21 mm |
325/30R23 | 30.7" | 780 mm | 23 mm |
325/35R22 | 31" | 787 mm | 22 mm |
325/40R21 | 31.2" | 793 mm | 21 mm |
325/60R15 | 30.4" | 771 mm | 15 mm |
345/55R16 | 30.9" | 786 mm | 16 mm |
355/25R24 | 31" | 788 mm | 24 mm |