Marathon Fueling Calculator
Gels, carbs and a race-day scheduleRuns locally · nothing uploaded
| Time | About | Take |
|---|---|---|
| 0:40:00 | 7 km | 1 gel + a few sips of water |
| 1:05:43 | 11.6 km | 1 gel + a few sips of water |
| 1:31:26 | 16.1 km | 1 gel + a few sips of water |
| 1:57:09 | 20.6 km | 1 gel + a few sips of water |
| 2:22:51 | 25.1 km | 1 gel + a few sips of water |
| 2:48:34 | 29.6 km | 1 gel + a few sips of water |
| 3:14:17 | 34.2 km | 1 gel + a few sips of water |
| 3:40:00 | 38.7 km | 1 gel + a few sips of water |
36–48 hours before: 650–780 g carbs per day (10–12 g/kg), with less fiber and fat.
1–4 hours before: a breakfast with 65–260 g carbs (1–4 g/kg, less the closer to the start) that you have tried in training.
General guidance based on sports nutrition consensus statements. Sweat rates and gut tolerance vary; consult a doctor or dietitian if you have medical conditions.
How it works
Formula
During the race: none needed under 75 min; 30–60 g/h for 1–2.5 h; 60–90 g/h beyond 2.5 hGels = carbs per hour × (hours − 0.5) ÷ carbs per gelUses the lower end of the range; first gel at about 40 min, none in the last 20 min.
Worked example
Given: Marathon in 4:00:00, 65 kg, 25 g gels
- Over 2.5 h, so 60 g/h.
- 60 × 3.5 ÷ 25 = 8.4 → 8 gels.
- Spread from 0:40 to 3:40, about every 26 minutes.
Result: 8 gels; 650–780 g carbs per day for carb loading.
Sources
- Thomas DT, Erdman KA, Burke LM. Med Sci Sports Exerc. 2016;48(3):543–568.
- Jeukendrup A. Sports Med. 2014;44(Suppl 1):S25–S33.
How to use
- 1Choose the race and enter your expected finish time and weight.
- 2Enter the carbs per gel and pick the weather.
- 3Follow the schedule and rehearse it on a long run first.
FAQ
How many gels for a marathon?
For about 4 hours with 25 g gels, roughly 7–9, starting around 40 minutes and every 25–30 minutes after. Trained athletes can take up to 90 g/h with gut training.
Should I take gels with water?
Usually yes; a few sips help absorption. Isotonic gels can be taken without water.