315/45R21 Tire Size Specifications & Compatible Vehicles
Overall Diameter
816.9 mm
Section Width
315 mm
Sidewall Height
141.8 mm
Circumference
2566.4 mm
Revs/Mile
627
Rim Diameter
21"
Inch Equivalent
32.2x12.4R21
Rim Width (ETRTO)
10.0" – 12.5"
Alternative Tire Sizes
These tire sizes are within 3% overall diameter of 315/45R21 and may be used as replacements:
Understanding 315/45R21
The tire size 315/45R21 means the tire has a section width of 315mm, an aspect ratio of 45% (the sidewall height is 45% of the width), and fits a 21-inch rim.
Sidewall Height = 315 x 0.45 = 141.8 mm
Overall Diameter = (141.8 x 2) + (21 x 25.4) = 816.9 mm
Circumference = 816.9 x π = 2566.4 mm
Overall Diameter = (141.8 x 2) + (21 x 25.4) = 816.9 mm
Circumference = 816.9 x π = 2566.4 mm
Frequently Asked Questions
The 315/45R21 is a standard tire size. Check your vehicle door jamb sticker or owner manual to confirm compatibility.
A 315/45R21 tire has an overall diameter of 816.9mm (32.2 inches). The sidewall height is 141.8mm, and the total circumference is 2566mm.
For 315/45R21 tires, the ETRTO recommended rim width is 11.0". The acceptable range is 10.0" minimum to 12.5" maximum. Using a rim outside this range can cause improper bead seating and unsafe handling.
Yes, as long as the replacement tire overall diameter is within 3% of the 315/45R21 816.9mm diameter. Compatible alternatives include 215/60R22, 235/55R22, 335/50R19. Use our Tire Size Calculator to compare any two sizes.