How Many Gels Do You Need for a Marathon? A Simple Timing Plan

For a 4-hour marathon, eight 25 g gels give you 50 g/hr of carbohydrate. Use eight 30 g gels instead and you're at 60 g/hr. Same number of packets, a different fueling plan.

So how many gels do you need? Multiply your practiced hourly carb target by your finish time, subtract any carbs you'll get from drinks or other food, then divide by the carbs in each gel. Round up when packing, and bring one spare separately.

All the counts below cover fuel during the race. Breakfast and an optional gel before the start sit outside that calculation. They're examples to rehearse, not a reason to double your intake on Sunday because the internet gave you a table.

Start with carbs per hour, not gel count

A gel is just packaging. The actual target is carbohydrate per hour.

The guidance changes with the length and intensity of the effort. Jeukendrup's review of carbohydrate intake during exercise describes around 60 g/hr for efforts lasting 2-3 hours, and up to 90 g/hr for longer efforts using multiple carbohydrate sources, such as glucose plus fructose. That's relevant to marathons, but it isn't a command to jump straight to 90.

The tables use 50 and 60 g/hr as practical worked examples. Your practiced target may be lower or higher. If you're already comfortable at 75-90 g/hr, use the same calculation with that number; this article doesn't impose a 60g ceiling.

That means the gel count changes fast:

Carbs in each gel	One every 30 minutes supplies
22 g	44 g/hr
25 g	50 g/hr
30 g	60 g/hr
40 g	80 g/hr

For a first marathon, I would rather see a runner execute 40-50 g/hr cleanly than write down 75 g/hr and spend the back half looking for bathrooms. But higher carb plans can work, especially with glucose-fructose products, and the glucose-to-fructose post explains why that only helps if the product and gut training match the target.

The gel is not the plan. The grams are the plan.

Gel count by finish time

Let's use a 25 g gel as the default.

This table assumes you're using gels as the main fuel source and taking water with them. But if you're also drinking meaningful sports drink, subtract those carbs instead of pretending they do not count.

Finish time	Total carbs at 50-60 g/hr	25g gels for 50 g/hr	25g gels for 60 g/hr
3:00	150-180 g	6	8
3:30	175-210 g	7	9
4:00	200-240 g	8	10
4:30	225-270 g	9	11
5:00	250-300 g	10	12
6:00	300-360 g	12	15

Packet counts round up to cover the target; the spare isn't included. That can leave a little extra. Eight 25g gels contain 200 g, for example, even when the calculated need is 180 g. You don't have to force down the remainder at the finish line. Spread your planned intake across the race, and check the actual grams in the schedule you've chosen.

That might look like a lot if you're used to taking one gel on a long run and calling it good.

But the math is not weird. A 4-hour runner targeting 60 g/hr needs 240 g total. With 30 g gels, that's eight gels. If they plan to get 60 g from sports drink across the race, six gels supply the remaining 180 g.

Body size is not a simple multiplier for during-race carbohydrate. The same review explains why these recommendations use grams per hour rather than grams per kilogram. That matters for smaller runners, including many women: don't automatically halve your fuel because you're lighter than the person beside you. Duration, effort, tolerance, and practice belong in the decision.

Average is a trap here. Use the table to get close, then test it.

How many SiS, Maurten, or GU gels?

The brand name isn't enough. SiS GO Isotonic and SiS Beta Fuel have very different carb counts, which is why swapping packets one-for-one can change your whole plan.

Product	Carbs per gel	Packets covering 200g	Packets covering 240g
SiS GO Isotonic	22 g	10	11
SiS Beta Fuel Energy	40 g	5	6
Maurten Gel 100	25 g	8	10
Precision Fuel PF 30	30 g	7	8
GU Original	21-23 g, depending on flavor	10 at 22g	11 at 22g

Those totals represent the four-hour examples above, with no other carb source and packet counts rounded up. They compare quantities, not product performance. Check the label on your actual flavor, especially caffeine content, and rehearse any change of product. Eleven GO gels and six Beta Fuel gels may cover similar carb totals, but that doesn't make them interchangeable for your stomach.

Six Beta Fuel packets here means the standard Energy gel, not six caffeinated Beta Fuel + Nootropics gels.

So if you're asking how many Maurten gels to carry for a four-hour marathon at 50 g/hr, the answer is eight Gel 100s plus a spare. The 100 in the name isn't 100 grams of carbohydrate. An expensive misunderstanding.

When to take each gel

Time beats mileage.

Mile-based plans look tidy on paper, but marathon courses are not paced like a treadmill. You might run mile 1 too fast, climb at mile 8, get stuck in crowd traffic, or slow in the final 10K. So if your plan says "gel every 5 miles," the actual timing can swing all over the place.

Start early, then use an interval that fits the packet. A first gel around 15-30 minutes is a practical scheduling choice to test, not a biological deadline.

For a gels-only plan, the arithmetic is:

Minutes between gels = carbs per gel ÷ hourly carb target × 60.

A 25 g gel at 50 g/hr works out to every 30 minutes. A 30 g gel at 60 g/hr also works out to every 30 minutes. A 40 g gel at that same 60g target works out to every 40 minutes. Using the same alert for all three would give you different hourly totals.

This is a planning interval, not a stopwatch law. Adjust the exact moments around water access and comfort, then check the total again. If drink mix supplies part of your carbs, space the gels around that contribution too.

Set watch alerts if you need them. Write times on your hand. Or tape a tiny schedule to the back of your bib if that works.

Because late-race you is not exactly the CFO of the operation.

Waiting until you feel low is the classic mistake. By the time your legs feel hollow and your brain starts negotiating walk breaks, you're not making a nutrition decision anymore. So you're doing damage control.

What changes if the course has sports drink

Course sports drink can help, but it makes the math fuzzier.

Check both the drink label and what the race actually serves. For a hypothetical drink containing 6 g of carbs per 100 mL, a 150 mL pour supplies 9 g. That's useful, but an unmeasured mouthful isn't a full labeled serving.

But the bigger issue is stacking.

A 25 g gel plus 15 g from sports drink is a 40 g feed. Count both. Combining them isn't automatically wrong, but it deserves a rehearsal rather than a surprise increase halfway through the race. The gut-training review discusses practicing carbohydrate and fluid intake to improve tolerance.

Follow your gel's directions. GU recommends a few sips of water; SiS GO Isotonic and Maurten Gel 100 don't require water to wash them down. That doesn't remove your need to drink during the race. Keep your fluid plan separate from the packet instructions.

So use sports drink as one of these:

• a planned carb source that replaces some gels
• a backup when you miss a gel or cannot stomach one
• a small top-up between scheduled gels

Do not use it as mystery bonus fuel. Mystery bonus fuel is how a good plan gets greasy fast.

The gels vs. chews vs. drink mix guide goes deeper on this, but the simple marathon answer is still gels plus water for most runners.

Want the gel schedule matched to your exact pace, weather, and carb target? Build a personalized carb, fluid, and sodium plan in about 60 seconds with the free EnduranceOS planner.

Gel schedules for a 3-, 4-, or 5-hour marathon

Let's make it concrete.

A gel every 30 minutes

Here are three versions of the same schedule. With 25 g gels, each averages 50 g/hr; with 30 g gels, each averages 60 g/hr. These examples assume no additional carbohydrate from sports drink.

Finish time	Gel times	Total gels
3 hours	0:15, 0:45, 1:15, 1:45, 2:15, 2:45	6
4 hours	Same first six, then 3:15 and 3:45	8
5 hours	Same first eight, then 4:15 and 4:45	10

The four-hour version gives you 200 g from 25g gels or 240 g from 30g gels. No mystery sports drink needed to make the arithmetic work. And it's simple enough to follow when the course gets loud and your legs start filing complaints.

A four-hour marathon with 40g gels

Six 40 g gels supply 240 g, averaging 60 g/hr over four hours. One evenly spaced example is 0:20, 1:00, 1:40, 2:20, 3:00, and 3:40. Bigger packets mean fewer wrappers, but you still need to test how a 40g serving feels while running.

If you've only practiced 30 g/hr, neither schedule is your race-day starting point. Build from what you tolerate in training runs. And if the race takes longer than planned, keep the practiced interval going rather than stopping because you've reached the last time on the card. That's another job for the spare.

For a 5-hour runner, the hard part is often boredom and stomach fatigue, not math. So you may want one or two chews as backup, or a gel flavor that does not make you question your life choices by mile 21.

Count caffeine separately

Caffeine can help endurance performance, but you don't need it in every packet. The ISSN caffeine position stand reports benefits commonly at 3-6 mg/kg, with potential benefits at lower doses and considerable individual variation. That range isn't a minimum you have to reach through gels.

But caffeine gels are easy to overdo.

If every gel has caffeine, a 7-gel marathon can quietly turn into a huge dose. That might feel great for 20 minutes, then your stomach starts sending strongly worded emails.

My boring marathon setup, if you've already practiced caffeine, would be:

• non-caffeine gels early
• one caffeine gel around 2-3 hours in, depending on finish time
• maybe one more late if you've practiced it and know your tolerance

Check the milligrams, including breakfast coffee and any pre-start gel. Late caffeine is one option, not a rule that makes earlier caffeine ineffective. The caffeine timing guide gets into the details.

What if gels stop working late?

They might.

Gut discomfort can make a perfectly counted plan hard to follow. The gut-training review supports practicing intake, and our gut training post translates that into sessions you can use before race day.

And not just on long runs either. Practice on regular workouts. Take a gel 25 minutes into a Tuesday tempo. Drink the same sports drink you expect on course. Try the caffeine gel on a controlled day instead of making race morning the science fair.

For mild discomfort, ease the pace and consider a smaller amount of a familiar fuel if you can tolerate it. Don't force gels or water through repeated vomiting or severe symptoms; stop and get race medical help. There's no prize for finishing the packet while ignoring the person carrying it.

Also check your pace. If you're running above what your gut can tolerate, the best gel plan in the world gets shoved down the priority list.

The mistakes that make gel plans fail

Starting too late. Your first gel at mile 10 is not a strategy. It's an apology.

Ignoring the product directions. Some gels call for water; others don't. Neither instruction tells you your whole-race fluid requirement.

Counting packets instead of carbs. A 20 g gel and a 40 g gel are not the same thing. Read the label.

Trying new gels on race day. The expo sample can wait. Same brand, same flavor, same timing.

Ignoring sports drink carbs. If the course drink has carbs and you're using it regularly, count it.

Carrying exactly the planned number. Bring one extra gel. You might drop one, miss a packet tear, or decide your late-race brain needs fewer decisions.

The goal is not to carry a pharmacy in your shorts. The goal is to have enough fuel that one tiny mistake does not turn into a death march.

My default answer

If you want the boring answer, here it is.

For a four-hour runner who has practiced 50 g/hr, eight 25 g gels on the half-hour schedule above is a straightforward plan. At 60 g/hr, eight 30 g gels cover the race instead. Different finish time or different packet? Do the multiplication before you fill your pockets.

Count sports drink, check caffeine separately, bring one spare, and practice the schedule until it feels automatic. The carb-loading guide covers the day or two before; this is the fuel you plan to use once you're running.

You do not need a genius gel strategy. You need a plan simple enough that you can still follow it when the mile markers get rude.

The EnduranceOS planner turns that into an hour-by-hour carb, fluid, and sodium plan for your race. It takes about 60 seconds, and it's free.

These are research-informed planning examples, not personalized medical advice. Practice changes in training and get individual guidance if a medical condition affects your fueling.