285/65R20 designates a tire 285 mm (11.2") wide with a sidewall 65% as tall as it is wide — about 185 mm (7.3") — mounted on a 20-inch wheel. That works out to an overall diameter of roughly 34.6", a circumference of about 108.7", and approximately 583 revolutions per mile. Exact figures vary slightly by manufacturer and tread design.
Of the 24 285/65R20 tire models we track, the most common category is all-terrain (21 models), followed by highway all-season truck (3) — a good indicator of the kind of vehicles and driving this size is designed for.