How much carbs per hour cycling: the 60/90/120 g/h decision.

Short answer: most cyclists fuel at 60 to 90 grams of carbs per hour. A gut-trained athlete on a dual-carb mix can sustain 100 to 120 g/h reliably. The 60 g/h ceiling that gets repeated everywhere is a single-carb (glucose-only) limit. Add fructose and the ceiling roughly doubles. That is the whole story; the rest is detail.

Where the 60 g/h number comes from

The 60 g/h ceiling is real, but it is a ceiling for one transporter. Glucose moves from your gut into your bloodstream through SGLT1, a sodium-dependent transporter that saturates near 60 g per hour. Any pure-glucose product (dextrose, glucose syrup, maltodextrin alone) caps there. Push past 60 and the excess sits in your gut, pulls water in, and you get bloating or worse.

Fructose takes a different door. It moves through GLUT5, which handles roughly 30 to 40 g/h once a rider has trained for it. Run both transporters in parallel and the combined ceiling lands near 100 to 120 g/h. The 1980s number was correct for the 1980s products.

Picking your number

Dose by ride duration, not bodyweight. Carb tolerance scales with practice and gut training, not size.

• Under 90 minutes: 30 to 60 g/h. Often you can finish on water and a single gel. Glucose-only is fine here.
• 90 minutes to 3 hours: 60 to 90 g/h. This is where most fondos, intervals, and weekend long rides land. Dual-carb starts to matter.
• 3 hours and longer: 90 to 120 g/h. Gran fondos, half-Ironman bikes, Alps tours, ultra-distance. Dual-carb is required. Gut training is required.
• Race day in heat: same carbs, add sodium. Sweat losses are the variable, not the carbs.

Why dual-carb actually works

The Jeukendrup lab spent the 2000s running variations of one experiment: ingest carbs during exercise, label them with carbon isotopes, measure how much oxidises and how much sits in the gut. Glucose alone topped out around 60 g/h of oxidation. Glucose plus fructose at roughly 2:1 (or its inverse 1:0.7 to 1:0.8) consistently produced higher oxidation rates, lower GI distress at high doses, and better time-trial performance in trained athletes (Jeukendrup, 2014, Sports Medicine).

The ratio does not have to be exact. Anywhere in the 1:0.7 to 1:0.8 glucose-to-fructose window seems to give the parallel-transporter effect. Open Mix 01 lands at 35 g maltodextrin to 25 g fructose, which is roughly 1:0.71. We picked it because the grammage rounds cleanly; the decimal is not sacred.

Training your gut

If you have been fueling at 40 g/h for years, do not show up to your event drinking 90 g/h. Your gut needs progressive overload like your legs. The protocol is simple: start at your current comfortable rate, add 10 g/h each week, do it on easy rides where GI distress is annoying but not catastrophic, and within 4 to 8 weeks you will handle 90 g/h without thinking about it. Pushing to 120 g/h adds another 4 to 8 weeks.

Signs you have adapted: you can finish a 3-hour ride on a 90 g/h dose with no bloating, no side stitch, no urgent post-ride toilet trip. The training adapts both gastric emptying and intestinal transporter density. The science calls it gut training; the experience is that one Sunday it just stops being a problem.

The 60 g/h myth in the wild

You will still see the 60 g/h ceiling repeated as if it were universal. It is on the back of many sachets, in many forum threads, and in plenty of older training books. The number is not wrong; it is incomplete. It is the limit for a one-carb product, which is what most of the older science was using. The category moved; the marketing did not.

If your current product is glucose-only or maltodextrin-only, you are stuck at 60 g/h no matter how hard you train your gut. The lever is the fructose, not the discipline. Add it and the door opens.

What to do tomorrow

• Pick a number for your next event based on the duration ranges above.
• Two weeks before, train at that rate on a long ride. Pay attention to what your gut does between hour two and hour three.
• If you are stuck under 60 g/h, switch to a dual-carb mix before training harder. The lever is the chemistry first.
• Salt is its own conversation. Start at 0.5 g sodium per bottle for hot rides, 0.3 g for cool ones, and adjust by sweat rate.

The Open Mix 01 sachet is 60 g of dual-carb mix at the 1:0.71 ratio if you would rather not weigh powders. If you would rather mix it yourself, the full recipe is on the homepage. Both are fine. The number you fuel at is the lever; what you put in the bottle is the chemistry.