How many carbs per hour should I eat during a marathon?

Updated August 26, 2026 · By the Runked team

Carbs per hour and gel count, by finish time

The table below is Runked's own arithmetic, built by taking the carbs-per-hour range from the two sources above and dividing by 25 grams per gel, the carbohydrate figure on the label of Maurten's Gel 100, to estimate a gel count. Actual gels vary by brand: GU's Original Energy Gel lists 21–23 grams per packet on its label, so the same target rate needs a few more of those to hit the same total. In each row, the low end of the 60–90 g/h figure is Jeukendrup's stated ceiling for a single carbohydrate source; the high end is the ACSM/AND/DC 2016 ceiling for exercise beyond roughly 2.5–3 hours, reachable with a glucose-fructose blend.

Sources: Thomas, Erdman and Burke, "Nutrition and Athletic Performance," Medicine & Science in Sports & Exercise, 2016, the joint position statement of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine; Jeukendrup, "A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise," Sports Medicine, 44(Suppl 1):S25–33, 2014.

What the two sources actually say

The ACSM/AND/DC 2016 joint position statement sets the duration-based bands: roughly 30–60 grams of carbohydrate per hour for exercise lasting 1–2.5 hours, and a ceiling of up to 90 grams per hour once exercise runs beyond about 2.5–3 hours. A 3:00 marathon already crosses that mark, putting it and any slower finish in the upper bracket. The statement covers exercise in general; it isn't limited to marathons, and it doesn't name gels, chews or drinks by brand.

The Jeukendrup 2014 review (published in Sports Medicine, part of a supplement issue) explains the physiology behind that higher ceiling. For exercise around one hour, the review notes that a carbohydrate mouth rinse or small amounts can produce a performance benefit without a large intake target. For exercise lasting roughly 2–3 hours, it states that a single carbohydrate source, glucose alone, for example, can be oxidized at rates up to approximately 60 g/h, and that this is the practical recommendation for exercise of that length. For ultra-endurance events, the review puts the recommendation higher, at approximately 90 g/h, and states this rate requires carbohydrate ingested as multiple transportable carbohydrates, since a single source cannot be absorbed and oxidized fast enough to reach it. Both sources reserve the higher ceiling for the longest efforts. The position statement defines that band by duration, beyond roughly 2.5–3 hours, which is what puts a 3-hour-or-slower marathon inside it; Jeukendrup's review names ultra-endurance events for the same 90 g/h figure, and both describe the same multiple-transportable-carbohydrate mechanism for exceeding the single-source ceiling. Glucose and fructose combined, close to a 2:1 ratio in the review's discussion, is the combination it discusses as raising oxidation well above that ceiling.

How to apply it on race day

1. Anchor your target to your expected finish time. Use the table above as a starting range; a 2:45 finisher and a 5:00 finisher are working from different points in the ACSM/AND/DC bands.
2. Read the label for the exact carbohydrate figure. Gel carbohydrate content isn't standardized; Maurten's Gel 100 lists 25 g, GU's Original Energy Gel lists 21–23 g, and other brands differ again.
3. If you're aiming above about 60 g/h, check for a glucose-fructose blend. Per Jeukendrup's review, a single-sugar gel is unlikely to let you use much more than 60 g/h; a labeled multiple-transportable-carbohydrate or 2:1 glucose:fructose product is what the higher end of the range assumes.
4. Rehearse the amount and timing in a long run first. A carbohydrate amount or product not tested before race day is a variable worth removing ahead of time; see the marathon taper guide for where a final long run with race-day fueling fits into taper week.

These figures come from sports-nutrition guidance written for generally healthy athletes. Talk to a doctor or registered dietitian before setting a carbs-per-hour target if you have diabetes, a diagnosed GI condition, or take a medication that affects blood sugar; the last question below covers that case.

Common mistakes fueling a marathon

• Assuming every gel has the same carbohydrate content. The gap between a 21-gram and a 25-gram gel adds up over a 4-hour race; the label states the actual figure directly.
• Trying a new gel, flavor or brand for the first time on race morning. Neither source addresses product tolerance directly; it's a separate risk from the carbs-per-hour numbers above.
• Chasing the 90 g/h ceiling with a single-sugar product. Per Jeukendrup's review, reaching that rate requires a multiple-transportable-carbohydrate blend, since a single carbohydrate source oxidizes at up to about 60 g/h on its own.
• Applying a flat carbs-per-hour number regardless of finish time. The ACSM/AND/DC bands are duration-based; a target set for a 4-hour marathon isn't the same one the statement gives for a sub-2:30 finish.

What to do next

Compare your fueling plan to your own last long run, not to what anyone else needs; in Runked the rank starts everyone at Bronze and only moves on your own runs. See how the running rank works. For what and when to eat in the hours before the start, see what to eat before a run. For fitting race-day fueling rehearsals into a full build, see the marathon training plan and the marathon taper guide.

Frequently asked questions