A half triathlon, commonly called a “half Ironman” or 70.3, is a three-sport endurance race covering 70.3 miles total: a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run (a half marathon). It’s exactly half the distance of a full Ironman triathlon and one of the most popular long-course endurance events in the world.
The Three Distances
The “70.3” name comes from adding up the three legs. USA Triathlon lists the official distances as 1.2 miles of swimming, 56 miles of cycling, and 13.1 miles of running. Each leg feeds directly into the next with no scheduled rest between them, though you do pass through a “transition area” where you switch gear. The time spent in transition counts toward your overall finish time.
For context, a half triathlon sits near the top of the standard distance ladder. Sprint triathlons cover roughly 16 miles total. Olympic-distance races total about 32 miles. A half triathlon more than doubles the Olympic distance, and a full Ironman doubles the half. Most people who sign up for a 70.3 have already completed at least one shorter triathlon, though it’s not a strict requirement.
How Long It Takes to Finish
Most amateur athletes finish a half triathlon in roughly 5 to 7 hours, depending on fitness, course terrain, and weather. Elite age-group racers can break 4.5 hours, while competitive professionals finish closer to 3.5 to 4 hours. Races typically enforce a cutoff time of 8 to 8.5 hours, meaning you need to maintain a pace that keeps you ahead of rolling time limits for each leg.
The bike leg takes up the largest chunk of time for almost everyone, usually 2.5 to 3.5 hours. The run follows at roughly 1.5 to 2.5 hours, and the swim typically takes 30 to 50 minutes for mid-pack athletes. Transition times add a few more minutes on top.
Calorie Burn and Fueling
Endurance athletes burn about 500 to 600 calories per hour during sustained effort. Over the course of a 5- to 7-hour half triathlon, that adds up to somewhere between 2,500 and 4,000 calories, roughly the equivalent of an entire day’s food intake burned in a single morning. For comparison, a full Ironman burns an estimated 8,000 to 10,000 calories.
You can’t replace all of those calories during the race, but you do need to eat and drink while riding and running. A common guideline is 50 to 100 calories every 30 minutes during exercise, typically from energy gels, chews, or sports drinks. Hydration matters just as much. Losing more than 2 percent of your body weight in fluid during a session can measurably hurt performance. Many athletes practice their fueling strategy during training so race day doesn’t bring any surprises to their stomach.
What You Need for Equipment
A half triathlon doesn’t require exotic gear, but the distances are long enough that comfort and fit become critical. The essentials are a road or triathlon bike, a helmet (mandatory in every sanctioned race), running shoes, goggles, and a swimsuit or tri suit. A tri suit is a single outfit designed to be worn across all three legs, so you don’t waste time changing clothes.
Wetsuits follow water temperature rules. In races governed by international or Olympic standards, wetsuits are allowed when the water is 68°F (20°C) or colder and mandatory below 57°F (14°C). Ironman-branded events use slightly different thresholds, so checking the specific race rules is worth the effort. Beyond the basics, many athletes invest in clip-on aero bars for the bike, a race belt for their bib number, and a fueling system (bottles, gels, or a hydration pack) they’ve tested in training.
Training Timeline and Volume
A typical training plan for a half triathlon runs 12 to 20 weeks, depending on your starting fitness. A structured 12-week base plan from USA Triathlon starts at about 9.5 hours per week and builds to around 14 hours per week by the final training block. That weekly load usually includes three swims, two to four bike sessions, three to four runs, and one or two strength workouts.
The real challenge is the long sessions on weekends. To prepare for a 56-mile ride, you’ll need bike rides of 3 to 4 hours at least a few times during training. Long runs build to 10 to 12 miles. Most coaches don’t have athletes rehearse the full race distance before race day, relying instead on cumulative fitness built across weeks of consistent training. If you’re coming from a running background, the swim often needs the most dedicated practice. If you’re a swimmer, the run volume will be the bigger adjustment.
Race Day Structure
Races almost always start early in the morning, often between 6:00 and 7:00 a.m. The swim may begin as a mass start (everyone enters the water at once), a wave start (groups go at staggered intervals based on age or gender), or a rolling start where athletes enter the water a few at a time. Open-water swimming in a crowd is one of the most unfamiliar experiences for newcomers, and practicing in open water before race day helps significantly.
After the swim, you run to the transition area (called T1), strip off your wetsuit if you wore one, put on your helmet and cycling shoes, and head out on the bike. After 56 miles of riding, you return to the transition area (T2), swap cycling shoes for running shoes, and start the half marathon. Aid stations on the bike and run course provide water, electrolytes, and sometimes energy gels or food. Crossing the finish line after all three legs is one continuous clock from the moment your wave starts.
World Championship Qualification
The Ironman 70.3 World Championship is the pinnacle event for the half-triathlon distance. Qualifying works through a slot system at individual 70.3 races throughout the year. The winner of each age group at a qualifying event automatically earns a slot to the world championship. If that person declines, the slot rolls to the second-place finisher, then the third.
Unclaimed slots enter a “performance pool” and are offered to the next-fastest athletes at that event using an age-graded formula. This roll-down process means that even if you didn’t win your age group outright, staying at the awards ceremony can pay off. Slots sometimes roll several places deep, especially in smaller or less competitive age groups. For most recreational athletes, though, simply finishing is the goal, and the race experience itself is the reward.