Run Fuel & Hydration Calculator
Get a practical starting target for fluid, sodium and carbohydrate intake based on your run duration, pace, body weight and temperature.
Your starting targets
These are practical estimates, not measurements of your individual sweat rate or sweat sodium concentration.
How this estimate works
Pace is used as a rough proxy for running intensity. Faster running generally increases metabolic heat production and carbohydrate demand. Body weight is used to scale the estimated fluid and carbohydrate requirements, while temperature shifts the hydration and sodium targets upward in warmer conditions.
For longer runs, the carbohydrate recommendation increases because maintaining carbohydrate availability becomes increasingly important. Sodium is estimated from an assumed sweat sodium concentration and the estimated fluid requirement.
The best way to personalize the fluid target is to measure your own sweat rate using body weight immediately before and after a representative run.
Triathlon Race Nutrition Planner
Create a customized race-day nutrition plan with detailed timing for carbohydrates, electrolytes, fluids, and caffeine based on your race distance and conditions.
How do you plan race nutrition for a triathlon?
A race nutrition plan translates race duration and body weight into a per-hour schedule of carbs (60–120 g/hr), fluid (500–1,000 ml/hr) and sodium (500–1,500 mg/hr) . The planner combines gels, drink mix and chews to hit targets without overfilling the stomach. Longer races need higher carb totals and more fluid; pacing and weather shift the number up or down.
- Sprint: 20–30 g carbs total (1 gel or none)
- Olympic: 30–60 g/hr on the bike and run
- 70.3: 70–90 g/hr — needs gels plus drink mix
- Ironman: 90–120 g/hr — multiple carb sources required
Plan Configuration
Your Personalized Nutrition Plan
Pre-Race Meal (3 Hours Before Start)
Total Race Nutrition
Race Day Timeline
Product Recommendations
Based on your carb target, here's what to bring:
Example calculation
Athlete:
70 kg triathlete, 70.3 race, 5h 30m, moderate temperature.
Pre-race (3 h out):
breakfast ~140 g carbs, 300 mg sodium, 500 ml fluid.
On-course target:
70 g carbs/hr × 5.5 h = ~385 g carbs
during the race.
Sodium on course:
800 mg/hr × 5.5 h = 4,400 mg.
Fluid on course:
800 ml/hr × 5.5 h = 4.4 L.
Common mistakes
- Waiting until hunger or bonk — by then the stomach has already shut down
- Only using one carb source — need glucose + fructose mix to absorb 70+ g/hr
- Skipping sodium on a cool day — muscle cramps still hit if sweat rate is high
- Not rehearsing the plan in a long training session — race day is the wrong time to find out you can't stomach it
How this calculator works
Carb, sodium and fluid targets per hour are derived from the athlete's body weight, race distance and ambient temperature, then split across pre-race fueling and on-course intervals.
Assumptions
- • Carb intake range of 30–120 g/hour scaled by race distance
- • Sodium scaled by temperature (cool / moderate / hot)
- • Single-loop nutrition plan — multi-loop courses may need re-spacing
Limitations
- • Always test fuelling at race pace before race day
- • Caffeine timing is generic — adjust to your tolerance
- • Does not account for altitude, drafting rules or special-needs bag drops
Who this is for
- • Triathletes building a sprint, Olympic, 70.3 or Ironman race-day plan
- • Athletes practising fuelling in long training sessions
- • First-timers who want a structured starting point
Who this is not for
- • Athletes with diabetes — work with a sports dietitian
- • Anyone with a clinical GI condition affecting carb absorption