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Marathon fueling plan by finish time

Carbs per hour, grams for the whole race, and when to take them. · 9 min read · Updated October 24, 2026

How we made this guide: we built it from the research below and checked every number against it: ACSM, Academy of Nutrition and Dietetics & Dietitians of Canada joint position stand (2016); Jeukendrup, carbohydrate intake during exercise (2014); Jeukendrup, training the gut (2017); Burke et al., carbohydrates for training and competition (2011); IOC consensus on supplements (2018); exercise-associated hyponatremia consensus (2015); and the gut-training trials and surveys cited in the text.

This guide is for runners with a marathon on the calendar who want a number to aim for. “Eat a gel when you feel like it” is the usual advice, and it leaves a lot of people guessing at mile 20. The research gives amounts per hour, and your goal finish time turns those amounts into a plan.

Carbs (carbohydrates) are the sugars and starches your muscles burn hardest in a race. A gel is a small packet of concentrated carbs you swallow while running. g/h means grams of carbs per hour. The amounts below come from published guidelines. The timing rules and gel schedules are ours, and we say so each time.

How does your finish time set your fueling plan?

Time on the course decides how much you need to take in. The joint position stand from the American College of Sports Medicine and two dietetics groups ties the carb target to how long you’re out (Thomas et al., 2016):

A 3:00 marathon sits right at the edge of that last row, and every slower finish is well inside it. So across the finish times below, the working range is 60–90 g/h. The 90 is the guideline’s ceiling. The 60 is our practical floor for long races, since 30–60 g/h is the guideline for shorter efforts.

One adjustment: a related review of these guidelines drew mostly on well-trained athletes and says to lower the amounts when your absolute effort is lower (Jeukendrup, 2014). A runner aiming for 5:00 may do well nearer the low end.

How many carbs per hour, and how many grams over the whole race?

Multiply your grams per hour by your hours on the course. Here are three rates for five finish times:

Calculated from the rates shown. 75 g/h is the midpoint, our suggested target once you’ve practiced. Drinks count toward the total. A 25 g gel is typical (Maughan et al., 2018), so check your brand’s label.

Which column should you pick? Ninety only works if your gut can absorb it. When the carbs come from glucose-type sugars alone, the muscles stop using more than about 60 g/h. Adding fructose, which is absorbed by a different route, raised that in lab studies by up to about 75% (Jeukendrup, 2014; Jeukendrup, 2017). Check your gel or drink label for glucose or maltodextrin plus fructose before you count on 90. If you’ve never fueled on long runs, start near 30–60 g/h and build from there.

Real-world intake often falls short of these ranges. In one survey of athletes after endurance events, marathon runners reported averaging about 35 g/h (Pfeiffer et al., 2012). More isn’t automatically better, though. In a 2022 trial, highly trained endurance athletes on a very high carb plan (90 g/h during the run, plus two weeks of high-carb eating and gut practice) improved performance about as much as a plan in the lower guideline range, so treat 90 as a ceiling for runners who have practiced it (King et al., 2022). For other race distances, see how many carbs per hour during a race.

What should you eat before the start?

Two meals shape your first miles. For events longer than 90 minutes, the guideline is 10–12 g of carbs per kg of body weight a day for the 36–48 hours before. On race morning it’s one breakfast of 1–4 g/kg, eaten 1–4 hours before the start (Thomas et al., 2016). Our rule of thumb is about 1 g/kg for each hour of lead time, so a 150 lb (68 kg) runner eating three hours out aims for about 200 g. Our guides cover both: how to carb load and what to eat before a race, with a table by body weight and timing.

If you use caffeine, the IOC consensus statement on supplements lists 3–6 mg per kg of body weight about an hour before, or smaller amounts (under 3 mg/kg) before and during exercise, taken with carbs. Doses of 9 mg/kg or more do not appear to add benefit and are more likely to bring side effects (Maughan et al., 2018). Many gels contain caffeine, so add it up, and try the dose in training first. Our caffeine guide has a table by weight.

Should you take gels by the clock or by the mile?

We’d take them by the clock. This is our rule of thumb, not a research finding. The studies measure intake in grams per hour. Mile markers come faster or slower as you climb, tire or get stuck in a crowd, and a watch alarm is one less decision at mile 22. With 25 g gels:

Example, a 4:00 goal at 75 g/h: set your watch to buzz every 20 minutes. Gels at 0:20, 0:40, 1:00 and so on through 3:40 are 11 gels, or 275 g, about 69 g/h across the four hours. Sports drink from aid stations covers the rest. A typical sports drink is 5–8% carbohydrate, so 500 mL carries roughly 25–40 g (Maughan et al., 2018).

Gels are concentrated, and concentrated carb solutions can slow how fast fluid is absorbed (Jeukendrup, 2014). We’d take each one with a few sips of water.

How do you train your gut for race-day fueling?

The gut adapts to what you ask of it. Stomach emptying and comfort can be trained, and a high-carb diet may raise the number of transporters that move sugar across the intestine wall (Jeukendrup, 2017). That review also reports that 30–50% of athletes regularly have stomach or bowel problems during sport.

Two small trials in runners put it to the test. In one, 25 runners spent two weeks repeatedly eating or drinking during exercise, in two carb groups and one placebo group. Both carb groups cut their stomach symptoms by about 60%, more than the placebo group (Costa et al., 2017). In the other, 18 runners did daily one-hour runs for two weeks taking either 90 g/h of carbs or a placebo, and the carb group ended with fewer symptoms than the placebo group (Miall et al., 2018). A 2023 systematic review of eight studies found gut discomfort tended to drop, while results for other symptoms were mixed (Martinez et al., 2023). The takeaway is to practice, and not to count on it fixing everything.

An example ramp for the last two months of training, ours and not from a study:

• Weeks 1–2: 30–40 g/h on your long run.
• Weeks 3–4: 45–60 g/h.
• Weeks 5–6: 60–75 g/h.
• Weeks 7 and on: your race target, on at least two long runs at goal pace.

Hold back if your stomach complains and repeat the week. Use your race products, in the same order, from the first week. The review also warns that low-carb eating or cutting calories hard may reduce your ability to absorb carbs on race day, and suggests including some high-carb days (Jeukendrup, 2017).

How much should you drink, and do you need electrolytes?

Sweat rates range from 0.3 to 2.4 liters an hour depending on effort, fitness and weather. The position stand’s typical plan is 0.4–0.8 L/h, adjusted to your tolerance, with the goal of losing less than 2% of your body weight (Thomas et al., 2016). To find your own rate, weigh yourself before and after a long run: a loss of 1 kg is roughly 1 L of sweat once you’ve counted what you drank and any bathroom stops.

Don’t overdo it. Drinking more than you sweat is the main cause of hyponatremia, a dangerous drop in blood sodium, and it is typically seen in recreational athletes, who sweat less than faster runners but often believe they need to drink more. The international consensus on the condition recommends drinking when thirsty (Hew-Butler et al., 2015). Before the start, 5–10 mL/kg over the previous 2–4 hours is the position stand’s guide, about 340–680 mL for a 150 lb runner.

Sodium is worth planning for. The position stand says to take it during exercise when you sweat more than 1.2 L/h, sweat salty, or run longer than 2 hours, which covers most marathon finishers. Sweat averages about 50 mmol/L of sodium (about 1 g/L), but it varies a lot between people. Sports drinks typically carry 10–35 mmol/L (Maughan et al., 2018), so read the label on yours. Cramps are usually tied to muscle fatigue, though they may also go along with dehydration and electrolyte imbalance (Thomas et al., 2016).

What do you do when fueling goes wrong?

• Your stomach feels full or sick. Stomach trouble is more likely in heat, when dehydrated, and after high-fiber or high-fat food or very concentrated drinks (Jeukendrup, 2017). Our approach: ease your pace a little, take only water for 10 minutes, then restart with half a gel.
• You missed a gel. Our advice is to take the next one on schedule and not double up. Past about 60 g/h from one sugar, the muscles don’t use more, and the extra may sit in the gut (Jeukendrup, 2017).
• You’re fading and behind on fuel. Start now, in small frequent amounts, rather than waiting for a better moment. This is our advice, based on the guideline tying higher intake to better performance in the longest events.
• It’s hot. Sweat and stomach trouble both rise. Practice in the heat if you can, and lower your target a notch rather than force it.
• You feel bloated, puffy, headachy or confused after lots of fluid. Those can be symptoms of low blood sodium, which needs prompt medical attention (Thomas et al., 2016). Stop drinking beyond thirst and tell the medical staff.

How do you test the plan before race day?

Rehearse the whole morning. On at least two long runs, eat your planned breakfast at your planned time, carry your race products and let the watch alarm do the timing. Afterward, write down the times, the grams and how your stomach and energy felt. The version that works becomes race day.

We built My Track Record so logging what you ate and drank on a run is one spoken sentence, and we estimate the carbs for you. Say the gels and the drink in the same sentence so they’re counted together. Add up the grams and divide by the hours to get your grams per hour.

By Andrew, founder of My Track Record. Andrew has been active all of his life across a variety of sports and continues to stay active through climbing, swimming, weight training, golfing, snowboarding, and more. He built My Track Record so logging food and training takes one spoken sentence and can support any activity. He puts these guides together from published sports science research cited on each page. About Andrew

Sources

• Thomas DT, Erdman KA, Burke LM. Nutrition and Athletic Performance: joint position statement of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada. Med Sci Sports Exerc. 2016;48(3):543–568. Source
• Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med. 2014;44(Suppl 1):S25–S33. Source
• Jeukendrup AE. Training the Gut for Athletes. Sports Med. 2017;47(Suppl 1):101–110. Source
• Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition (IOC Consensus Conference on Nutrition in Sport). J Sports Sci. 2011;29(Suppl 1):S17–S27. Source
• Maughan RJ, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455. Source
• Costa RJS, et al. Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Appl Physiol Nutr Metab. 2017;42(5):547–557. Source
• Miall A, et al. Two weeks of repetitive gut-challenge reduce exercise-associated gastrointestinal symptoms and malabsorption. Scand J Med Sci Sports. 2018;28(2):630–640. Source
• Martinez IG, Mika AS, Biesiekierski JR, Costa RJS. The effect of gut-training and feeding-challenge on markers of gastrointestinal status in response to endurance exercise: a systematic literature review. Sports Med. 2023;53(6):1175–1200. Source
• King AJ, et al. Short-term very high carbohydrate diet and gut-training have minor effects on gastrointestinal status and performance in highly trained endurance athletes. Nutrients. 2022;14(9):1929. Source
• Pfeiffer B, et al. Nutritional intake and gastrointestinal problems during competitive endurance events. Med Sci Sports Exerc. 2012;44(2):344–351. Source
• Hew-Butler T, et al. Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clin J Sport Med. 2015;25(4):303–320. Source

General information for healthy adult runners, not medical advice. If you have a medical condition, are pregnant, or have a history of disordered eating, talk to a doctor or registered dietitian before changing how you eat, drink or use caffeine.

Related

• How many carbs per hour during a race
• What to eat before a race
• How to carb load for a half or full marathon
• Race week fueling timeline
• Race fuel calculator
• What to eat after a long run