How Many Carbs Per Hour for Endurance?
A practical guide to carbohydrate intake for long runs and rides — the 30–60–90 g/hour framework, why the glucose-to-fructose ratio matters past 60 g, and how to train your gut.
Carbohydrate is the limiting fuel in most endurance racing. Your muscles and liver store only enough glycogen for roughly 90–120 minutes of hard effort, so once you go longer than that, what you eat during the effort largely decides whether you hold pace or fade. The good news is that the targets are well established and easy to plan around.
The 30–60–90 framework
How much carbohydrate you can use per hour depends mostly on how long and how hard you are going, and on how much your gut is used to being fed:
| Duration / intensity | Carbs per hour | Carb type |
|---|---|---|
| Up to ~1 hour | 0–30 g (often none needed) | Any |
| 1–2.5 hours | 30–60 g | Glucose / maltodextrin is fine |
| 2.5 hours and beyond, or hard | 60–90 g | Glucose + fructose mix |
Why the ratio matters past 60 g
Glucose crosses the intestinal wall through a transporter called SGLT1, which saturates at around 60 g per hour — eat more pure glucose than that and the excess just sits in your gut and causes distress. Fructose uses a separate transporter (GLUT5), so combining the two carbohydrates opens a second lane and lets total absorption reach 90 g per hour or more. That is why modern sports drinks and gels advertise a glucose-to-fructose ratio such as 2:1 or 1:0.8.
Turning grams into real food
Most gels carry 20–25 g of carbohydrate, a 500 ml bottle of sports drink around 30 g, and a typical chew about 4–5 g. So 60 g per hour might be two gels, or one gel plus a bottle of drink. Spread intake across the hour rather than taking it all at once, and always wash gels down with water.
Use the carbohydrate fuelling calculator to turn your race duration and target rate into an hour-by-hour intake plan, and the sweat-rate calculator to match your fluid intake to how much you actually lose.
Train your gut
The gut adapts to what you ask of it. Athletes who practise high-carb fuelling in training tolerate far more on race day than those who only fuel when racing. Start at the low end of the range, rehearse your exact race-day products on long sessions, and build the rate up over weeks. The biggest fuelling mistake is trying a new, aggressive intake for the first time on race morning.
Questions
How many carbs per hour should I aim for?
For efforts up to about 2 hours, 30–60 g of carbohydrate per hour is usually enough. Beyond 2–3 hours, or at high intensity, work up toward 60–90 g per hour using a mix of glucose and fructose. Untrained guts should start at the low end and build up.
Why can I absorb more than 60 g/hour only with mixed carbs?
Glucose is absorbed through the SGLT1 transporter, which saturates near 60 g/hour. Adding fructose, which uses a different transporter (GLUT5), opens a second pathway so total absorption can reach 90 g/hour or more.
Can I train my gut to take more carbs?
Yes. Regularly practising race-day fuelling in training increases intestinal transporter capacity and reduces GI distress, so the gut is a trainable organ much like the heart or legs.