How many carbs per hour in a marathon
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Why carbohydrate matters so much
At marathon pace your body burns mostly carbohydrate. Glycogen stores in muscle and liver are limited, and for many amateurs they run low in the last 10–12 km. That is when pace collapses even though the legs still feel fit.
Taking carbohydrate while running does not refill the stores, but it slows how fast they empty and keeps blood glucose stable. That is why the main sports nutrition guidelines recommend it for any endurance event over an hour.1
How much, by race duration
| Race duration | Carbs per hour | Type |
|---|---|---|
| Under 1 hour | Not needed | A mouth rinse at most |
| 1–2.5 hours | 30–60 g | Glucose or maltodextrin is enough |
| Over 2.5 hours | Up to 90 g | Glucose and fructose mixes |
The 60 g per hour ceiling with glucose alone comes from the gut: the transporter that absorbs it saturates. Fructose uses a different route, so a mix of the two lets you absorb more with fewer stomach problems.2
Some professionals now go beyond 90 g per hour. A 2026 review argues the ceiling could rise to 120 g per hour, at least in trained athletes, while the 120–200 g/h seen in the field is not yet backed by studies.5 That is data on athletes who have trained for it over time, not on amateurs: for amateurs it is not a good starting point.
A 2026 study of 15 trained male cyclists and triathletes compared 60 and 100 g of carbohydrate per hour during 240 minutes of intermittent cycling. After the protocol, performance in a 15-minute time trial dropped by 9.3% with 60 g/h and by 6.4% with 100 g/h; final muscle glycogen did not differ between conditions.6 The sample is small, all male, on a bike, and the protocol does not match a marathon: it is not a prescription for amateurs.
Before the race
Loading. In the 36–48 hours before the marathon, guidelines suggest 10–12 g of carbohydrate per kg per day.1 For a 70 kg runner that is 700–840 g a day, more than it sounds. Cutting back on fibre and fat makes it easier to manage without feeling heavy.
Breakfast. 1–4 g per kg, 1 to 4 hours before the start, with smaller amounts the closer you get to the gun.1
In practice: a 3:30 marathon
Worked example, not a prescription: with a 3 hour 30 minute goal and 60 g per hour, that is 3.5 × 60 = 210 g of carbohydrate over the whole race. With 25 g gels, 210 / 25 = 8.4 gels: rounding to 8 gels gives 200 g, about 5% under the total. Gel timing is decided around the start and aid stations. If you take sports drink at aid stations, count the grams of carbohydrate the product states and subtract them from the total: you need fewer gels. The right amount for you depends on gut tolerance, body weight and intensity, and is settled by trying it in training.
Moving towards 75–90 g per hour can help, but only if you have rehearsed it several times in long runs at race pace.
Work out your own numbers with the carb calculator.
Training the gut
The stomach adapts: taking carbohydrate regularly in training increases how much you can absorb and reduces discomfort.3 Use the long runs of the last 8–10 weeks to test the hourly amount, the gel brand and the timing, ideally with the same products you will find at the aid stations.
How we reviewed it
Document review of the sources: sports nutrition guidelines and reviews on carbohydrate absorption.
Limits. Intakes above 90 g/h concern habituated athletes and are not a starting point for recreational runners. The 120 g/h idea comes from a 2026 review and is not proven in the field.
Related tool: Wolf Engine, Fuel.
Sources
Sources rechecked on 26 October 2026. The 2016 guidelines are older but not outdated for that reason: the 2026 review discusses them and proposes a higher ceiling for trained athletes. These are practical recommendations, not a personal plan.
- Thomas, Erdman, Burke. American College of Sports Medicine joint position statement on nutrition and athletic performance. Medicine & Science in Sports & Exercise, 2016. Link
- Jeukendrup. Review of carbohydrate intake during exercise and how to personalise it. Sports Medicine, 2014. Link
- Jeukendrup. Review on training the gut in athletes. Sports Medicine, 2017. Link
- Burke, Hawley, Wong, Jeukendrup. Carbohydrates for training and competition. Journal of Sports Sciences, 2011. Link
- Narrative review on carbohydrate intake during endurance exercise. The Journal of Nutrition, 2026. Link
- Mazza et al. Carbohydrate intake of 100 vs. 60 g/h during prolonged cycling in male endurance athletes. Medicine & Science in Sports & Exercise, 2026. Link