275/70R18 designates a tire 275 mm (10.8") wide with a sidewall 70% as tall as it is wide — about 193 mm (7.6") — mounted on a 18-inch wheel. That works out to an overall diameter of roughly 33.2", a circumference of about 104.2", and approximately 608 revolutions per mile. Exact figures vary slightly by manufacturer and tread design.
Of the 103 275/70R18 tire models we track, the most common category is all-terrain (75 models), followed by highway all-season truck (22) — a good indicator of the kind of vehicles and driving this size is designed for.