A standard Olympic-distance triathlon covers 51.5 kilometers (about 32 miles): a 1.5 km (0.93 mi) swim, a 40 km (24.8 mi) bike ride, and a 10 km (6.2 mi) run, completed in that order. This is the distance used at the Olympic Games, where triathlon debuted at Sydney 2000. The format was created in the mid-1980s by race director Jim Curl.
Source: Wikipedia, Triathlon