Triathlon Nutrition Calculator

Triathlons are prolonged multi-sport events that deplete glycogen stores rapidly. Without adequate fueling, athletes risk 'bonking' — a sudden and severe drop in energy caused by low blood sugar. Proper nutrition maintains performance across all three disciplines and supports recovery between training sessions.

During a race, focus on fast-digesting carbohydrates such as energy gels, chews, bananas, and sports drinks. Aim for 30–90g of carbohydrates per hour depending on race duration and intensity. Avoid heavy, solid foods that slow digestion and cause GI distress.

Begin carbohydrate loading 2–3 days before your race by increasing carb intake to ~8–10g per kg of body weight per day. On race morning, eat a familiar, high-carb, low-fiber meal 2–3 hours before the start. Experiment with your nutrition plan during training — never try anything new on race day.

Calorie needs depend on your body weight, race distance, and finish time. A general rule is to replace 25–30% of calories burned per hour during races lasting under 90 minutes, and up to 60–70% for longer events like the Ironman. This calculator estimates your burn and recommended intake based on your inputs.

Most athletes should target 400–800ml of fluid per hour, depending on heat, humidity, and sweat rate. During the swim, hydration is not possible, so it's important to be well-hydrated beforehand. Focus your drinking strategy on the bike and run legs.

No — eating or drinking during the swim leg is not practical or safe. Your swim nutrition strategy should consist of arriving at the start well-hydrated and with adequate glycogen stores. Begin consuming carbohydrates and fluids as soon as you mount your bike.

A Sprint triathlon lasts roughly 60–90 minutes for most athletes and may require little to no mid-race fueling beyond hydration. A Full Ironman can take 9–17 hours, demanding a detailed nutrition strategy with hundreds of grams of carbohydrates, thousands of calories, and careful fluid and electrolyte management throughout.

More efficient athletes (advanced/elite) tend to burn slightly fewer calories at the same speed due to better movement economy. However, they often race at higher intensities, which increases total calorie expenditure. Beginners may burn more calories per kilometer due to less efficient form, particularly in swimming and running.