Most runners need somewhere between 6 and 12 gels for a full marathon. Your number depends on your finish time, how many carbs are in each gel, and how much carbohydrate you also take from sports drink. The quick formula: pick your hourly carb target (60 g is a solid starting point), multiply it by your hours on the course, then divide by the carbs per gel. We walk through the maths, a ready-made table, and how to adjust it for Singapore’s heat below.
TL;DR
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Aim for 30 to 60 g of carbohydrate per hour, and build toward up to 90 g per hour if you have trained your gut.
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With a typical 25 g gel, that works out to roughly 2 to 3 gels per hour. A 4-hour marathon usually means 8 to 10 gels, depending on your target and any drink carbs.
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Do the maths: (carbs per hour × race hours) ÷ carbs per gel. Our table below does it for you.
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Practise the exact plan in long runs, in warm and humid conditions, for several weeks before race day.
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In Singapore’s humidity, plan to carry your own gels and pair them with fluids and sodium, rather than relying on aid stations alone.
Table of Contents
Why the number varies so much between runners
Search this question and you will see answers from “5 to 8 gels” to “8 to 12 gels”. Neither is wrong. They assume different finish times, different gel sizes and different carb targets.
Three things set your number:
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Time on course. A 3-hour runner and a 5-hour runner need very different totals, even at the same hourly rate.
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Carbs per gel. Most gels give 20 to 30 g of carbohydrate, so one gel covers roughly a third to a half of an hour’s needs. Always read the label on the pack you plan to use.
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Hourly target. This is the big one, and it is where the research has moved in recent years.
How many carbs per hour should you aim for?
The common marathon range is 30 to 60 g of carbohydrate per hour. Runners who have practised “training the gut” may handle up to 90 g per hour, especially with a glucose and fructose mix.
For events over about 2.5 hours, guidance goes higher: 60 to 70 g per hour, up to 90 g per hour if tolerable, taken in small, regular amounts to spare glycogen. The same source reports that athletes who met the 60 to 90 g per hour target were much more likely to finish in under 180 minutes, regardless of sex, age or experience.
Most runners under-fuel. Jeukendrup’s write-up of a 2010 study found marathoners averaged only about 35 g per hour. It also describes a Copenhagen Marathon study in which runners who followed a science-based plan of roughly three gels per hour finished 4.7% faster than those who chose their own intake, with no significant stomach problems.
Our take: start at 60 g per hour as your race-day goal. Move toward 75 or 90 g only after your stomach has shown it can take it in training.
The simple formula
Gels needed = (carbs per hour × hours of running) ÷ carbs per gel
Example: you expect 4 hours, you want 60 g per hour, and your gel has 25 g.
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60 × 4 = 240 g of carbohydrate
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240 ÷ 25 = 9.6, so 10 gels
If you also take some carbs from sports drink at aid stations or from your own bottle, subtract those grams first. Fewer gels, same fuel.
Marathon gel table (25 g gels)
This table uses our own arithmetic from the formula above. It assumes every carb comes from a 25 g gel, and rounds up to the nearest whole gel. Treat it as the ceiling; drink carbs reduce it.
| Finish time | 40 g/hour | 60 g/hour | 75 g/hour |
|---|---|---|---|
| 3:00 | 5 gels | 7 gels | 9 gels |
| 3:30 | 6 gels | 9 gels | 11 gels |
| 4:00 | 7 gels | 10 gels | 12 gels |
| 4:30 | 8 gels | 11 gels | 14 gels |
| 5:00 | 8 gels | 12 gels | 15 gels |
A few notes on reading it:
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The 40 g column suits runners who are new to fuelling or have a sensitive stomach and are building up.
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The 60 g column is the sensible race goal for most people running over 2.5 hours.
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The 75 g column is for runners who have trained at that rate and tolerated it. Many Singapore runners choose a middle path, with some gels and some drink.
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If your gels are 20 g or 40 g, rerun the formula. Larger gels mean fewer of them.
How often should you take a gel?
Spacing matters as much as the total. For an average runner, one Singapore newspaper feature recommends a gel every 30 to 45 minutes. Your glycogen stores last about two hours, so the aim is to start before you need it.
The maths of spacing with 25 g gels, from a Singapore marathon fuelling guide:
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One gel every 30 minutes gives 50 g per hour.
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One every 25 minutes gives 60 g per hour.
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One every 20 minutes gives 75 g per hour.
RUN Singapore suggests taking your first gel around 60 to 75 minutes in. Many runners aiming for higher hourly targets start earlier and use shorter gaps. What matters is that you have rehearsed your own schedule. Set a watch alert for each gel so you never have to think about it when you are tired. A Garmin smart watch makes this easy with custom reminders.
Water or no water with your gel?
This depends on the type of gel. RUN Singapore notes that most hypertonic gels should be taken with water to avoid stomach discomfort, while isotonic gels can be taken without. Check the pack and test it in training. Taking a concentrated gel with a mouthful of water at each aid station is a simple habit that protects your stomach.
Adjusting your plan for Singapore’s heat and humidity
Running here is not the same as running in a cool European spring. A 2025 review reports that hot and humid conditions raise carbohydrate use and sweat rate, and that the combination worsens gut discomfort, dehydration and sodium loss.
What that means in practice:
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Carry your own gels. Do not plan to rely on aid stations for every gel. Pack your full supply in a race belt or shorts pockets.
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Expect your stomach to be touchier. Heat diverts blood flow toward your skin. Lean toward the lower end of your tested range if you have never run a hot race on your plan.
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Add electrolytes. Gels contain some sodium and potassium, but long, sweaty races often call for more. Our guide to electrolyte balance during a marathon covers it in detail, and you can browse our hydration range when you plan your bottles.
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Do not overdrink. The ACSM position, as summarised in the Singapore fuelling guide, is to avoid losing more than 2 percent of body weight to sweat, and World Athletics warns against drinking beyond your sweat losses. Weigh yourself before and after a long training run to learn your own sweat rate.
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Rehearse in the heat. Do your key long runs at similar times and in similar humidity to your race.
For a full picture of what to do in the two days before a humid race, see our Singapore marathon fuelling plan.
Gut training: how to work up to 60 to 90 g per hour
Your gut adapts to carbohydrate just like your legs adapt to mileage. In a 2023 study, a two-week repetitive carbohydrate feeding protocol reduced gut discomfort by an average of 47%. A 2025 systematic review also found that two weeks of purposeful carbohydrate intake during running lowered the severity of GI symptoms.
A practical build-up for your long runs:
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Weeks 1 to 2: Start at a comfortable rate, such as 40 to 45 g per hour (roughly 2 gels per hour or a gel plus a drink).
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Every second week: Add 10 to 15 g per hour while your stomach stays settled. A Singapore guide suggests building over eight to ten weeks, starting at 60 g.
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Final long runs: Rehearse your exact race plan, including brand, flavor, timing and fluids, in conditions as close to race day as possible.
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Race week: Change nothing. No new gel, no new flavor.
For a deeper dive, read our gut training tips for marathon runners. If your stomach is the sticking point, our guide to energy gels for a sensitive stomach helps you choose and test.
If stomach symptoms during runs are frequent or severe, see a sports dietitian or your doctor, who can assess what is going on and tailor a plan to you.
Practise race-day eating beyond gels
Gels are one tool, not the whole plan. Training-day meals shape how well you tolerate fuel on the run. If you want a framework for building meals around your training load, these reusable meal templates for athletes show how to portion plates and think in grams per hour. Pair that with tested gels, and you cover both sides of the equation.
Worked examples
Example 1: the 3:30 runner. You want 60 g per hour for 3.5 hours, so 210 g in total. You will take two cups of sports drink (about 9 g each, per the Singapore fuelling guide) at a few stations, for roughly 36 g. That leaves about 174 g, or 7 gels. Carry 8 and keep one spare.
Example 2: the 4:30 first-timer. You are still building tolerance, so you start with 45 g per hour. Over 4.5 hours that is about 203 g, or around 8 gels of 25 g. Take one every 30 minutes with water, skip the very first minutes, and have one more in reserve. In your next block, you can raise the target slightly.
Example 3: the sub-3:00 runner. At 75 g per hour for 3 hours you need 225 g, which is 9 gels. That is a gel roughly every 20 minutes. Only attempt this if you have practised it, because the high rate is for trained stomachs.
Do not forget what happens before the start
Your race-day gels sit on top of a carbohydrate-loaded start. RUN Singapore recommends raising carbohydrate intake to about 70% of daily calories in the final 1 to 3 days. Our carb loading guide for marathons shows how to do it without feeling bloated. Many runners also take one gel 5 to 10 minutes before the gun, as long as they have tried it in training.
Perspective
Every season, we hear the same worry from runners: “I do not know if I am taking too many gels, or too few.” Our advice is to stop guessing and start measuring. Work out your carbs per hour, divide by the carbs in your gel, and write the number on your hand or your watch.
We built Racepack to make that easier. We are an official retailer for the gel brands we carry, which matters because you want to know the product in your belt is genuine and has been stored properly. Our next-day delivery within Singapore also means you can restock for a long run without disrupting your schedule.
Our view is simple: the best gel plan is the one you have practised. Choose a gel you enjoy, start at a level you can handle, and build up week after week. Your best marathon begins in training, long before race day.
Jason John
Choose your gels and get race-ready
We stock energy gels from leading international brands, all available with next-day delivery within Singapore and guaranteed authenticity. Here is how we would match them to your plan:
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Maurten Gel 100: a non-caffeinated 4-pack that is easy to test in training, and to count out for race day.
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SiS BETA Fuel: a caffeinated gel with nootropics for runners who want caffeine late in the race.
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GU Roctane: an assorted pack to try several flavors during your long runs.
For recovery after the finish line, browse our recovery powders and protein powders. If you want to understand what is inside your gel, read our guides on energy gel ingredients, how gels are absorbed, and our full energy gels guide for endurance athletes. To see how elite fuelling looks, read how Sabastian Sawe fueled a sub-2 London Marathon.
Race-week checklist
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Calculate your gel total with the formula, then add one or two spares.
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Pack gels in order of use, so you do not have to think mid-race.
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Set watch alerts for each gel time.
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Carry electrolytes and know which aid stations have water.
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Use only gels and flavors you have already tested.
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Finish your last long run at least a couple of weeks out so your legs, and your stomach, are rested.
FAQ
How many energy gels do I need for a full marathon?
Most runners need 6 to 12 gels, depending on finish time and carbs per gel. A 4-hour runner aiming for 60 g per hour with 25 g gels needs about 10 in total, or fewer if some carbs come from sports drink. Use the formula in this guide to get your own number.
How often should I take a gel during a marathon?
A common range is one gel every 30 to 45 minutes for an average runner, according to The Business Times. If you are targeting 60 g per hour with 25 g gels, that tightens to about every 25 minutes. Start early rather than waiting until you feel tired.
When should I take my first gel?
RUN Singapore suggests around 60 to 75 minutes into the run. Some runners take one 5 to 10 minutes before the start as well. Whichever you choose, rehearse it in your long runs.
How many carbs per hour do I need in a marathon?
Aim for 30 to 60 g per hour as a common range. Trained runners may work up to 90 g per hour for events over 2.5 hours. Build up gradually in training.
Should I take gels with water?
Most hypertonic gels should be taken with water to avoid stomach discomfort, while isotonic gels can be taken without, per RUN Singapore. Check your gel’s label and test it on your long runs.
Can too many gels upset my stomach?
Yes, if your gut is not used to the volume. Research shows that two weeks of repeated carbohydrate intake during exercise reduced gut discomfort on average. Build up slowly, and see a sports dietitian or doctor if symptoms persist.
Do I need more gels in Singapore’s heat?
Heat and humidity raise carbohydrate use and sweat rate, but they can also make your stomach more sensitive. Rather than simply adding gels, rehearse your plan in warm conditions, add electrolytes and carry your own supply.
Can I use gels and sports drink together?
Yes. Count the carbs from both toward your hourly target and reduce the number of gels accordingly. Sports drink cups at aid stations add roughly 9 g each, according to a Singapore fuelling guide.
Where can I buy genuine energy gels in Singapore?
We are an official retailer for the brands we carry, with guaranteed authenticity and next-day delivery within Singapore. Browse our energy gels and hydration range to build your race-day supply.
Sources
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Marathon fueling: get it right before, during and after – Sports Performance Bulletin
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The Effect of Gut-Training and Feeding-Challenge on Markers – PMC
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Nutritional strategies for minimizing gastrointestinal symptoms – PMC
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