How Many Gels for a Marathon?
A complete guide to marathon gel timing, quantity, and race day fueling strategy.
The short answer: most marathoners running for a goal time need between 6 and 10 gels during a marathon, including one taken 15 minutes before the start. The exact number depends on your goal time, body weight, and how aggressively you're racing.
The longer answer involves understanding why gels matter, how many carbs per hour you actually need, and how to space them out so your stomach doesn't revolt at mile 18.
Why You Need Gels in a Marathon
Your body stores roughly 1,500 to 2,000 calories of glycogen in your muscles and liver. A marathon at goal pace burns somewhere between 2,400 and 3,200+ calories depending on your size and intensity. That means you're going to run out of stored energy somewhere between mile 18 and 22 — the infamous "wall."
Gels bridge that gap. Each standard gel (like a Maurten Gel 100) delivers about 25 grams of carbohydrates and 100 calories. By taking them consistently throughout the race, you're topping off your fuel tank before it hits empty.
This isn't optional for anyone chasing a time goal. You can run a casual 5K or 10K on water alone. A marathon at race effort? You need fuel.
How Many Carbs Per Hour?
Current sports science recommends 60 to 90 grams of carbohydrates per hour for marathon-effort running. Most runners targeting a sub-3 to sub-3:30 marathon should aim for the higher end of that range — around 55 to 65 grams per hour from gels alone.
At 25 grams per gel, that works out to roughly one gel every 25 to 30 minutes during the race.
Key insight: The marathon is a fueling competition disguised as a running race. You can have elite-level cardiovascular fitness and still blow up if your fueling plan is wrong. This is the most common mistake among ambitious amateur marathoners.
Gel Count by Goal Time
Here's a general guide based on race duration. These assume one pre-race gel plus gels every 25 minutes during the race:
| Goal Time | Race Duration | Gels During Race | Total (incl. pre-race) |
|---|---|---|---|
| 2:50 – 2:59 | ~2h 55m | 6 | 7 |
| 3:00 – 3:09 | ~3h 05m | 6–7 | 7–8 |
| 3:10 – 3:19 | ~3h 15m | 7 | 8 |
| 3:20 – 3:29 | ~3h 25m | 7–8 | 8–9 |
| 3:30 – 3:44 | ~3h 37m | 8 | 9 |
| 3:45 – 3:59 | ~3h 52m | 8–9 | 9–10 |
When to Take Your First Gel
Take your first gel 15 minutes before the gun goes off. This tops off your blood glucose right at the start without requiring you to fumble with a gel packet while dodging other runners in the opening miles.
Your second gel (first during the race) should come around 30 minutes in — typically around mile 3 to 4 for sub-3 runners. Then every 25 minutes after that.
Caffeinated vs. Non-Caffeinated Gels
Most runners benefit from alternating caffeinated and non-caffeinated gels. The standard approach is to make every other gel caffeinated, starting with gel 3 or 4. This spreads your caffeine intake across the race rather than front-loading it.
A typical caffeinated gel has about 50 to 100 mg of caffeine. Research supports total caffeine intake of 3 to 6 mg per kilogram of body weight for endurance performance — for a 160-lb runner, that's roughly 200 to 430 mg total across the race.
The Mistake Almost Everyone Makes
Most first-time marathoners (and many experienced ones) undereat during the race. They take 3 or 4 gels when they need 7 or 8. They skip the pre-race gel. They wait too long to start fueling and by the time they feel low on energy, it's too late to recover.
The other common mistake: not training your gut. If you've never taken gels during training runs, do not show up on race day and slam 7 of them. Your stomach needs practice processing fuel while running at effort. Start incorporating gels into your long runs at least 8 weeks before race day.
What About Hydration and Sodium?
Gels are only one piece of the puzzle. You also need to manage fluid intake (16 to 28 fl oz per hour depending on conditions and sweat rate) and sodium (500 to 1,100 mg per hour depending on weather and how much you sweat).
Hot conditions mean more fluid and more sodium. Cool conditions mean you can back off. This is why a static fueling plan doesn't work — you need to adjust for race day conditions.
Build Your Exact Gel Schedule
Our Race Day Fueling Calculator builds a personalized gel schedule, fluid plan, and sodium strategy based on your weight, goal time, sweat level, and race day weather.
Get Your Fueling Plan →Quick Checklist
- One gel 15 minutes before the start
- First race gel at 30 minutes (around mile 3–4)
- One gel every 25 minutes after that
- Alternate caffeinated and non-caffeinated
- Practice with gels during long training runs
- Carry your own — don't rely on course nutrition
- Wash down each gel with a few sips of water
The difference between a great marathon and a death march often comes down to fueling. Get the gel count right, practice it in training, and execute on race day.