275/65R20 designates a tire 275 mm (10.8") wide with a sidewall 65% as tall as it is wide — about 179 mm (7.0") — mounted on a 20-inch wheel. That works out to an overall diameter of roughly 34.1", a circumference of about 107.0", and approximately 592 revolutions per mile. Exact figures vary slightly by manufacturer and tread design.
Of the 82 275/65R20 tire models we track, the most common category is all-terrain (59 models), followed by highway all-season truck (19) — a good indicator of the kind of vehicles and driving this size is designed for.