Nutrition.
Race-day fueling and hydration plan. Carbs, fluids, sodium per hour — plus a gel-by-gel timeline tuned to your finish time.
RACE
04 h
00 m
°F
YOU
lbs
PROJECTED PACE · MARATHON
5:41
min/km·3,585 kcal·75 g carbs/hr
CARBS/HR
75 g
FLUID/HR
500 ml
SODIUM/HR
400 mg
GELS NEEDED
10
FUELING TIMELINE
- 7.9 km@ 45 minGel #1 + 250ml water
- 13.2 km@ 1:15Gel #2 + 250ml water
- 18.5 km@ 1:45Gel #3 + 250ml water
- 23.7 km@ 2:15Gel #4 + 250ml water
- 29 km@ 2:45Gel #5 + 250ml water
- 34.3 km@ 3:15Gel #6 + 250ml water
- 39.6 km@ 3:45Gel #7 + 250ml water
Schedule assumes start of fueling at ~45 min. Test in training, never on race day.
METHODOLOGY
How this calculator works
- Carbohydrate intake during endurance exercise
Recommended intake during a marathon is 60–90 g/hour of mixed carbohydrates (glucose + fructose). Below 60 g/hour, performance drops late in the race. Above 90 g/hour, GI distress rises. PaceCalc estimates per-hour intake by your weight and predicted finish time.
A. E. Jeukendrup, "A step towards personalized sports nutrition: carbohydrate intake during exercise," Sports Medicine, vol. 44, suppl. 1, 2014, pp. 25–33.
NOTES
- Pre-race carb-loading guidance (8–12 g/kg body weight in the 24 hours before) is standard sport-science practice. Individual GI tolerance varies a lot — practice your race-day fueling in long runs first.
FAQ
Frequently asked
- When should I start fueling during a race?
- Start taking in carbs around 45 minutes into the race, before you feel depleted. Then continue every 30-45 minutes. Waiting until you 'hit the wall' is too late — prevention is far more effective than cure.
- How many carbs per hour do I need?
- For races under 2.5 hours: 30-60g/hr. For longer races: 60-90g/hr. Gut training is essential — practice your fueling strategy during long training runs to find your tolerance level.
- How much water should I drink during a marathon?
- Generally 400-800 ml per hour depending on conditions. In hot weather (>25°C/77°F), aim for the higher end. Avoid over-drinking — hyponatremia (low sodium) from excessive water is dangerous.
- Do I need electrolytes during a race?
- Yes, especially for races over 90 minutes. Aim for 300-600 mg sodium per hour (more in heat). Many gels and sports drinks contain electrolytes, but you may need additional sodium in hot conditions.
- Should I fuel differently for a triathlon?
- Yes! On the bike you can absorb more (60-90g carbs/hr) because of less GI stress. On the run, reduce to 30-60g/hr. Front-load your nutrition on the bike to reduce fueling needs during the run.