How many gels for a marathon?
How many gels for a marathon? The real answer comes down to three numbers: your target time, your carbs-per-hour goal, and the carbs per gel. The maths is simple: race duration × carbs/hour ÷ carbs per gel. Example: a 4-hour marathon at 60 g/h with 25 g gels works out to roughly 9 to 10 gels. This guide walks through how to set each of those three numbers for your profile — and why most runners carry too few rather than too many.
How many gels, and when to take them
During the race, a common starting point is 30 to 60 g of carbs per hour; well-trained runners at higher intensities can target 60 to 90 g/h. Beyond roughly 60 g/h, glucose + fructose blends earn their keep: the two sugars use distinct intestinal absorption pathways, letting you take in more without saturating a single route. In practice: start early (first gel around 30-45 minutes, not halfway), then one gel every 25 to 40 minutes depending on dosage. Take each gel with water rather than a sports drink, to avoid an overly concentrated mix in your stomach.
Before the start: topping up
Before the race, the goal is to start with full glycogen stores: a final carb-rich meal 3 to 4 hours before the gun, optionally topped up with a gel or fruit purée in the last 15 minutes. Count your gels the night before, adding 1 to 2 spares in case of a drop or an unexpected need. Don't count on aid-station gels you've never tested — an unknown brand at the 25 km mark is a risky bet.
Your fuelling timeline
Standard plan — 4-hour Marathon (60 g/h target with 25 g gels)
Before: pre-race meal + optional pre-start snack
During: ~60 g/h carbs + 500-600 ml/h water
After: recovery drink for quick rebuilding
Pre-race cake or bread + honey
+ 500 ml water
1 easy-to-digest gel
or energy fruit purée
Standard energy gel
+ 150 ml water
Standard energy gel
+ 150 ml water
Standard energy gel
+ 150 ml water
Standard energy gel
+ 150 ml water
Caffeine gel (75-100 mg)
+ 150 ml water
Standard energy gel
+ 150 ml water
Recovery drink
Protein + carbs
This plan uses 6 gels during the race. Carry 1 or 2 extra spares in your running belt.
After the finish
After the finish, the priority is reloading and rehydrating: carbs plus protein within the hour helps kick-start recovery, along with water and some sodium to replace losses. It's also the moment to write down what worked — how many gels, at which kilometres, and which ones sat well. Those notes are gold for the next marathon.
Your plan in 5 points
- Gel count computed: target duration × g/h ÷ g per gel
- 1 to 2 spare gels on top of the calculation
- Brand and flavours already validated in training
- Intake plan set (first gel at 30-45 min, then regular intervals)
- Water planned with every gel
The mistakes that cost you
- Taking the first gel too late (halfway instead of within the first 45 minutes)
- Relying on aid-station gels you've never tested in training
- Washing gels down with concentrated sports drink instead of water
- Calculating your stock on an optimistic finish time — a slower marathon needs more gels
- Copying another runner's plan without accounting for your own gut tolerance
FAQ
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