305/45R20 Tire Size Specifications & Compatible Vehicles
Overall Diameter
782.5 mm
Section Width
305 mm
Sidewall Height
137.3 mm
Circumference
2458.3 mm
Revs/Mile
655
Rim Diameter
20"
Inch Equivalent
30.8x12R20
Rim Width (ETRTO)
9.5" – 12.0"
Alternative Tire Sizes
These tire sizes are within 3% overall diameter of 305/45R20 and may be used as replacements:
Understanding 305/45R20
The tire size 305/45R20 means the tire has a section width of 305mm, an aspect ratio of 45% (the sidewall height is 45% of the width), and fits a 20-inch rim.
Sidewall Height = 305 x 0.45 = 137.3 mm
Overall Diameter = (137.3 x 2) + (20 x 25.4) = 782.5 mm
Circumference = 782.5 x π = 2458.3 mm
Overall Diameter = (137.3 x 2) + (20 x 25.4) = 782.5 mm
Circumference = 782.5 x π = 2458.3 mm
Frequently Asked Questions
The 305/45R20 is a standard tire size. Check your vehicle door jamb sticker or owner manual to confirm compatibility.
A 305/45R20 tire has an overall diameter of 782.5mm (30.8 inches). The sidewall height is 137.3mm, and the total circumference is 2458mm.
For 305/45R20 tires, the ETRTO recommended rim width is 10.5". The acceptable range is 9.5" minimum to 12.0" 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 305/45R20 782.5mm diameter. Compatible alternatives include 325/50R18, 275/50R20, 295/55R18. Use our Tire Size Calculator to compare any two sizes.