How Many Carbs Per Hour for an Ultra? The 60-90 g Guide, Gut Training and Worked Hourly Plans

For most ultrarunners the answer is 60 grams of carbohydrate per hour as the floor you train toward, 90 grams per hour as a ceiling worth building to if you race hard and have a cooperative gut, and something in the 40 to 70 gram range in the back half of a 100-miler, when intensity is low and tolerance is what limits you. Above roughly 60 grams per hour you need more than one carbohydrate type (glucose plus fructose) to absorb it, and whatever number you pick has to be rehearsed on long runs for six to ten weeks before it will work on race day. This is general sports-nutrition education, not a prescription: practice it in training, and if you have a medical condition, talk to a sports dietitian or physician before changing how you fuel.

Where the 60 to 90 gram numbers come from

Carbohydrate absorbed from the gut reaches the blood through transporters in the intestinal wall. The glucose transporter saturates at roughly 60 grams per hour, which is why decades of advice capped intake there. Fructose uses a different transporter, so a mix of glucose (or maltodextrin, or dextrose) and fructose (or sucrose, which is half fructose) lets the body oxidize up to around 90 grams per hour. This is the basis of the "multiple transportable carbohydrate" guidance now found in the major sports-nutrition position stands, and of the 2:1 glucose-to-fructose ratio on so many labels. Some newer products use a ratio closer to 1:0.8, on the reasoning that a little more fructose improves oxidation and reduces gut symptoms at high intakes.

The headlines about elite marathoners and cyclists consuming 100 to 120 grams per hour are real, but they describe two-to-four-hour events run near threshold by athletes who trained their guts for it. An ultra is a different problem. You are moving at a lower intensity, burning proportionally more fat, and staying out for 8 to 36 hours. The ceiling matters less than the floor, and the floor is set by what you can keep eating at hour 14.

Why ultras are not just long marathons

A mid-pack runner at ultra effort burns somewhere between 500 and 800 calories an hour depending on size, terrain and pace. Nobody replaces that. The goal of race fueling is not to match expenditure; it is to keep blood glucose steady and spare enough glycogen that you never enter the deficit spiral where low energy makes you nauseous, nausea makes you stop eating, and stopping eating makes you slower and colder. Sixty grams of carbohydrate is 240 calories, and holding that steadily for hours does more for a 100K than 400 calories in one sitting followed by nothing.

Three things push ultra targets below the textbook 90:

• Intensity. At a walk-run effort you cannot use 90 grams an hour, and unused carbohydrate sits in the gut.
• Heat. Blood flow shifts to the skin, the gut slows, and concentrated fuel becomes a liability. Hot-race plans run lower carbohydrate concentration and higher fluid.
• Descents and duration. Hours of downhill pounding and a tired diaphragm make the stomach less tolerant late in a race. Plans that start at 80 grams per hour commonly settle at 50 after dark.

Pick a target by race, then adjust for you

The table below is a starting framework, not a rule. Bodyweight matters less than you would expect, because absorption is limited by transporters rather than size; smaller runners tend to sit at the low end of each range simply because their intensity-for-pace differs.

Race	Typical duration	Starting target	Notes
50K, runnable	4 to 8 h	60 to 90 g/h	Highest intensity; drink-first plans work well
50-mile or 100K	9 to 18 h	50 to 80 g/h	Rotate sweet and savory from the first aid station
100 miles	20 to 36 h	40 to 70 g/h	Front-load daylight hours; expect a night dip
Hot conditions (any)	any	Drop 10 to 20 g/h	Dilute drink mix, lean on water plus electrolytes

Pick the number you will train, not the number you wish you could do. A runner who has rehearsed 65 grams an hour on ten long runs will beat a runner who plans 90 and manages 30.

Gut training: six to ten weeks, one session a week

The gut adapts. Research on "training the gut" shows that repeated exposure to carbohydrate during exercise increases transporter capacity and reduces symptoms, and that the adaptation happens over weeks, not days. A practical protocol used by many coaches:

1. Start four to ten weeks out. Pick one long run per week as the fueling rehearsal.
2. Begin at 40 to 50 grams per hour if you have never fueled deliberately. Add roughly 10 grams per hour every one or two weeks until you reach the race target.
3. Use race products only. The same drink mix, the same gel brand, the same savory items you will pack in drop bags.
4. Rehearse the hard parts: eating on climbs, eating right after a long descent, eating in the heat of the afternoon, eating while power-hiking.
5. Practice fluid too. A 500 ml flask an hour sloshing on a stomach that is not used to it produces the same nausea as too much sugar.
6. Do at least two rehearsals at race duration intensity: a back-to-back weekend or a long race-pace effort.

If you want the training side laid out in full, Jason Koop's Training Essentials for Ultrarunning devotes real space to fueling and gut training within a periodized plan, and it is the reference most coaches point to for the reasoning behind these numbers.

Worked hourly plans, math shown

Every plan below states its assumptions so you can swap in your own products. Tailwind's Endurance Fuel is used as the drink-mix example because it is the powder most often on aid-station tables, and its label is simple: per scoop, roughly 100 calories, 25 grams of carbohydrate from a dextrose-and-sucrose blend, and roughly 300 milligrams of sodium (check the current bag for exact numbers). A typical energy gel is about 22 to 25 grams of carbohydrate. Rounding is deliberate.

Plan A, 60 grams per hour, drink-first (runnable 50K, mild weather):

• One 500 ml flask per hour mixed with 1.5 scoops of Tailwind Endurance Fuel: about 37 g carbohydrate, about 450 mg sodium.
• One gel at the half hour: about 25 g.
• Hourly total: about 62 g carbohydrate, about 250 calories, about 450 to 500 mg sodium, 500 ml fluid.

Plan B, 75 grams per hour, mixed sources (100K, daytime):

• Flask one, 500 ml with 2 scoops of Tailwind: 50 g carbohydrate, about 600 mg sodium.
• Flask two, 500 ml plain water with an electrolyte add-in such as the Andros Sport hydration amplifier, which lets you raise fluid and sodium without raising carbohydrate concentration on hot climbs. Count its label sodium in the hourly total.
• One gel or half a sleeve of chews: about 25 g.
• Hourly total: about 75 g carbohydrate, about 300 calories, 1 liter of fluid, sodium of 600 mg plus whatever the add-in contributes.

Plan C, 50 grams per hour, real-food night plan (100-miler after dark):

• 500 ml with 1 scoop of Tailwind: 25 g carbohydrate, about 300 mg sodium.
• Aid-station food: a cup of broth plus a quarter of a PB&J or two boiled potato chunks with salt: roughly 20 to 30 g carbohydrate.
• Hourly total: about 45 to 55 g carbohydrate, warm calories that go down when gels will not, and sodium from the broth on top of the mix.

Notice what changes across the plans: the carbohydrate concentration of the drink goes down as the race goes on, fluid stays roughly steady, and the savory share goes up. That is the shape of a plan that survives to the finish.

Fluid and sodium, briefly

Fluid needs are individual and depend on sweat rate; 400 to 800 ml per hour covers most runners in most conditions, with the top of the range reserved for heat. Sweat sodium concentration varies enormously between people, from a few hundred to well over a thousand milligrams per liter, which is why a single sodium rule does not exist. The workable approach is to drink to thirst plus a plan, salt your food at aid stations, and keep the drink mix in the 4 to 8 percent range (20 to 40 g of carbohydrate per 500 ml) unless you have practiced stronger. Weighing yourself before and after long training runs tells you more about your own sweat rate than any calculator.

Signs the plan is wrong, and the aid-station reset

Under-fueling shows up as a slow fade three to five hours in, irritability, feeling cold, and the sudden conviction that you do not want to eat. That last one is the trap: it is a symptom of low fuel, not a reason to skip it. The fix is small and immediate, such as a gel and water at the next walk break, not a big meal.

Over-fueling or over-concentration shows up as sloshing, bloating, burping and nausea. Slow down for ten minutes, sip plain water, walk a climb, and switch the next hour to diluted drink or savory food. At the next aid station, run the reset: refill with a weaker mix, eat broth or fruit, and leave with something in hand. The 90-second aid-station routine covers the stop itself.

Execution: make the plan automatic

• Pre-measure scoops into small zip bags, one per flask refill, and put them in the vest and in every drop bag.
• Set a repeating alarm every 20 to 30 minutes. The COROS PACE 3 does this natively with a nutrition alert, and a beep beats willpower at hour 12.
• Write the hourly plan on a card taped inside the drop-bag lid, so the crew can restock to the plan rather than to what you say you want.
• Track intake by count, not by feel: three gels and two flasks in the last three hours is a fact; "I have been eating fine" is not.
• Rotate flavors and textures from the first aid station, before you are sick of anything.

Sixty grams an hour rehearsed is the goal. Ninety is a bonus for those whose training earns it. The runner who eats steadily at hour 20 is usually the one who practiced eating at hour 4, every week, for two months.