Most runners we talk to buy too few gels — and then take them too late.
It is an easy mistake. A box looks like plenty until you do the arithmetic against your finish time. Here is the maths, distance by distance, with the honest caveat that the textbook number is higher than what most people can actually stomach.
Start from carbohydrate per hour, not gels
Fuelling guidance is written in grams of carbohydrate per hour, because that is what your gut can absorb. For events lasting more than about 2.5 hours, the widely cited range is 60–90g per hour.
Our gels contain 26g of carbohydrate per 40g sachet. So:
- 60g/hour ≈ 2.3 gels per hour
- 90g/hour ≈ 3.5 gels per hour
That is more than most runners expect, and it is where the honesty needs to come in.
The textbook number vs what people actually manage
The 60–90g/hour range assumes a gut that has been trained to absorb it. Carbohydrate tolerance is a trainable capacity, not a fixed trait — and most recreational runners who have never practised it sit closer to 40–60g per hour before things get uncomfortable.
So there are two numbers: the one you should build towards, and the one you should start at. Both are below.
Distance by distance
| Distance | Typical finish | Gels — starting out | Gels — gut trained |
|---|---|---|---|
| 10K | 45–60 min | 0–1 | 1 |
| Half marathon | 1:45–2:15 | 2–3 | 4–5 |
| Marathon | 4:00–4:30 | 5–7 | 9–12 |
A few notes on reading that table.
For a 10K, you mostly do not need fuel at all — under an hour, your stored glycogen covers it. One gel 15 minutes before the start is about topping up and getting a caffeine lift, not about fuelling mid-race.
For a half marathon, this is where under-fuelling starts to show. Two hours at even 50g/hour is 100g of carbohydrate. Most runners take one gel and wonder why the last 5km felt so heavy.
For a marathon, the gap between textbook and reality is widest. Nine to twelve gels sounds absurd if you have never done it — but the reason elite marathoners take that many is that it works. If you are starting out, plan 5–7 and take them on a schedule, not when you feel bad. By the time you feel bad, you are already 20 minutes behind.
Do not forget you also need to train with them
This is the number almost everyone forgets.
Nothing new on race day is the oldest rule in endurance nutrition, and it means your race-day gels are not your only gels. If you are marathon training, you have perhaps 4–6 long runs where you should be rehearsing your exact fuelling plan — same gels, same timing, same conditions.
That is another 3–5 gels per long run. Realistically:
- Race day: 5–7 gels
- Long-run rehearsals: 12–25 gels across the block
Our gels come in boxes of 6 sachets. One box is roughly a single marathon's race-day fuelling at the lower end — which means if you are actually training for one, you want more than a box.
The Singapore adjustment
Two things change in local conditions.
You need more fluid and electrolyte, not more carbohydrate. Sweat rates well over a litre an hour are common here. That is a hydration problem, not a fuelling one — which is what Ultimate Hydro 50 is built for, carrying 67g of carbohydrate alongside sodium, potassium, magnesium and calcium in one pouch. If you are using it, count its 67g towards your hourly carbohydrate total.
Your gut gets less blood. Heat diverts blood to the skin for cooling and away from digestion. This is why gel texture matters more here, and why the same plan that worked on a cool morning can fall apart at 32km on a humid race day. Practise in the conditions you will race in — for most local races, that means early morning or evening, not an air-conditioned treadmill.
For a deeper breakdown of timing and electrolytes, see our guide to fuelling a marathon in Singapore's heat.
A simple starting plan
If you want one plan to test on your next long run:
- One gel 15 minutes before you start.
- One gel every 40 minutes after that, taken with fluid — set a watch alarm, do not go by feel.
- Note what happened. Adjust the interval to 30 minutes next time if you handled it comfortably.
That is roughly 40–50g/hour, which is a realistic starting point, and it builds towards the higher end over a training block.
Frequently asked questions
How many energy gels do I need for a marathon?
If you are new to structured fuelling, plan 5–7 gels taken on a schedule. Runners who have trained their gut for higher carbohydrate intakes commonly take 9–12. Our gels contain 26g of carbohydrate each, and the general guidance for events over 2.5 hours is 60–90g per hour.
How many gels for a half marathon?
Two to three is a reasonable starting point for a 1:45–2:15 finish, rising to four or five once you are comfortable at higher carbohydrate intakes. Most runners under-fuel half marathons and feel it in the last 5km.
Do I need a gel for a 10K?
Usually not. Under about an hour of running, stored glycogen covers you. One gel before the start can still help, mostly for the caffeine rather than the carbohydrate.
When should I take my first energy gel?
About 15 minutes before the start, then at regular intervals — every 30–40 minutes depending on what you have practised. Take them on a timer rather than waiting until you feel like you need one.
How many gels are in a box?
Six 40g sachets per box, which is roughly one marathon's race-day fuelling at the lower end of the range. If you are training for a race, budget separately for the long runs where you rehearse your plan.
Can I take too many energy gels?
The limit is your gut, not a safety ceiling. Going well beyond what you have practised commonly causes nausea, bloating or worse — which is why carbohydrate tolerance should be built gradually in training rather than attempted for the first time on race day.
Both our caffeinated and caffeine-free gels carry the same 26g of carbohydrate per sachet and are Informed Sport certified. Not sure which to pick? Read the caffeine guide.