Triathlons typically come in 4 different formats - Sprint, Olympic, Half-Iron, and Iron distances. While distances vary widely, these are the basic guidelines. 

• A Sprint distance involves anywhere from 400-825 yards of swimming, 10-15 miles of cycling, and usually 3 miles of running.
• The Olympic distance format is twice that of the sprint, and is also known as the international distance. It involves a 1.5K (.9 miles) swim, 40K (24.9 miles) bike, and 10K (6.2 miles) run. This is the official distance for Triathlon in the Olympics, hence the name Olympic distance.
• The Half-Iron distance (also known as long-course) is a little more than twice that of the Olympic distance, except for the swim portion. It involves 1.2 miles of swimming, 56 miles of cycling, and 13.1 miles of running.
• The next distance of racing is the Iron distance (also known as Ultra), and it is twice the distance of the Half-Iron. It consists of 2.4 miles of swimming, 112 miles of cycling, and 26.2 miles of running. Ouch!