⏵ Nutrition guide · Free

How to Build an Ultramarathon Fueling Plan (Hour by Hour)

To build an ultramarathon nutrition plan you work in five steps: figure out your finish time, set your hourly targets (roughly 60 to 90 g of carbs, 16 to 32 oz of fluid, and 300 to 1000 mg of sodium per hour), pick foods your gut can actually handle, map that intake onto each aid station and drop bag, then rehearse the whole thing on long runs and tweak it. The plan is a structure you eat to until your gut says otherwise, not a rigid contract. I will walk you through every step, give you sample 50K and 100 mile schedules, and at the end there is a free calculator that builds the plan for you.

Step 1: Set your hourly targets

Everything in an ultra fueling plan is built per hour. Start with these ranges, then make them yours: your weight, your sweat, the heat, and how trained your gut is. These are starting points to test in training, not guarantees.

Per hour	Target range	How to think about it
Carbohydrate	60 to 90 g/hr	If your gut is not trained for it you top out near 60. Run a glucose + fructose blend (about 1:0.8 to 2:1) and put in a few weeks of gut training and you can push the ceiling to 90, and some people get 100 to 120 in on hard mountain sections.
Calories	200 to 400 kcal/hr	You are burning 600 to 900+ kcal/hr and you are not going to eat that much back, your stomach will not let you. So you run a deficit on purpose. The job is to slow the bleed, not stop it.
Fluid	16 to 32 oz/hr (about 0.5 to 1.0 L)	Drink to thirst and to the day you are having. The low end is a cool day, the high end is heat and a lot of sweat. You want to land in the middle and stay off both extremes, dried out on one side and waterlogged on the other.
Sodium	300 to 1000 mg/hr	Figure roughly 500 to 1000 mg per liter of fluid. If you sweat salty or the day is hot, go higher. Salt follows your fluid, so the more you drink the more you salt.
Caffeine	50 to 100 mg every 1 to 2 hrs (optional)	Save it for the back half and the overnight low. Burn it early and there is nothing left for you when you really need a lift deep in the race.

For the deep dives behind two of these numbers, see how many carbs per hour you need and how much sodium per hour you need.

Step 2: Choose foods you can actually stomach

Hitting 60 to 90 g of carbs an hour for hours on end on nothing but gels is how you end up sick of the taste with a gut that has quit on you. The runners who finish strong mix exact products with real food that is low in fiber, a little salty, and not too sweet. Here are the staples that tend to sit well, and roughly what each one brings.

Food	Carbs	Why it works
PB&J on white bread or tortilla	~30 to 40 g per half	Low fiber, easy to chew, and a little fat and protein on top. The classic thing to reach for late in a race.
Boiled / salted potato	~25 to 30 g each	Salty, easy on the stomach, and warm at night. A good savory reset for when sweet has stopped working.
Banana	~25 to 31 g	Soft, fast carbs and some potassium. Goes down easy early, can sit heavy very late.
Broth (chicken, miso, ramen)	~5 to 15 g per cup	Sodium, warmth, and a break from sugar in your head. This is the thing that saves people overnight.
Salted rice balls / rice cakes	~30 to 40 g each	Plain, savory, and gentle on the gut. A solid thing to stash in a drop bag for long carries.
Chips, pretzels, salted snacks	~15 to 20 g per handful	Crunch, salt, and easy calories for when your mouth wants nothing to do with another sweet gel.
Gels / chews / drink mix	~20 to 25 g each	Exact numbers and easy to carry. Lean on these early, then mix in real food as the hours pile up.

A sweet-to-savory shift over the day is normal and expected. If your stomach is the thing that keeps blowing up, read how to avoid stomach problems during an ultra (and train your gut).

Step 3: Map fuel to aid stations and drop bags

An hourly target does you no good until you pin it to the real course. This is the step most runners skip, and it is exactly where plans fall apart.

Turn the aid station chart into carries

Pull the official aid station chart and write down the mileage of each station and the gap to the next one. Then figure out how long each gap takes at a realistic pace for that terrain. A long, climby carry can run three hours even if it is only nine miles. Now you know what you have to carry out of each stop.

Load each carry with enough carbohydrate and sodium to cover those hours at your hourly target, plus a little buffer in case you are slower than you planned. A two hour carry at 80 g/hr means leaving with around 160 g of carbohydrate on you. Run out of food two miles short of an aid station and you will pay for it for the next hour.

Drop bags carry what the course cannot

Aid stations will reliably have water, electrolyte drink, soda, fruit, chips, and often broth and potatoes, so you do not need to carry those. Use drop bags for the stuff the course will not have: your specific gels and chews, salt capsules, caffeine, a spare headlamp and battery, dry socks, lip balm, and any savory food you know you will be craving late.

Put a little fuel card in each drop bag and on your bottle: at THIS aid station, do THESE things. Swap bottles, grab your gels for the next carry, take a salt cap, top off on broth. Thinking gets hard at hour 20, so make the calls now, while your head is clear.

Step 4: Write the hour-by-hour schedule

Here is what a real plan looks like for two common distances. A 50K is roughly a 4 to 8 hour effort and you fuel it a lot like a long marathon. A 100 miler is a phased, all-day-and-night plan where the numbers come down on purpose as the hours stack up.

Sample 50K schedule (about a 6 hour effort)

Phase	Carbs	What to eat
Hours 0 to 2	60 to 70 g/hr	Gels or drink mix, sip fluid every 15 to 20 min, and get sodium going right away.
Hours 2 to 4	60 to 80 g/hr	Keep the gels going and grab a banana or half a PB&J at the aid station to break up all the sweet.
Hours 4 to finish	50 to 70 g/hr	Whatever still goes down: cola, chews, a few chips. Take caffeine now if you want a lift.

Sample 100 mile schedule (about a 24 to 30 hour effort)

Phase	Carbs	What to eat
Hours 0 to 4 (front-load)	70 to 90 g/hr	Bank carbs while your gut is fresh: gels, drink mix, banana. Keep sodium and fluid steady.
Hours 4 to 10 (daytime)	60 to 80 g/hr	Move toward solids: PB&J, potato, rice ball at every aid station. Push fluid and salt when it gets hot.
Hours 10 to 18 (evening + overnight)	50 to 75 g/hr	Go savory: broth, soup, quesadilla, chips. Take 50 to 100 mg of caffeine as the low hits. Keep eating small and often.
Hours 18 to finish (final push)	30 to 60 g/hr	Survival mode: get ANY calories in. Sip cola, take broth, nibble a potato. Go liquid carbs when solids quit on you.

100 mile cutoffs usually sit around 30 to 36 hours, so most runners are fueling for a full day and night. For how long that day actually runs, see how long it takes to run a 100 mile race, and for race-specific heat and night strategy on a real course, the Angeles Crest 100 guide.

Step 5: Adjust for heat, terrain, pace, and the night

The ranges above are your baseline. Race day conditions move them, and the back half of a long race moves them again.

Heat raises fluid and salt, lowers tolerance

In the heat your fluid needs climb toward the top of the 16 to 32 oz range and your sodium climbs right along with them, while your gut handles less solid food. So you drink and salt more, eat a touch less and go more liquid, and you practice fueling in that same heat first, so race day is not the first time your stomach has to deal with all of it at once.

A hot, exposed course is exactly where most well-trained runners fade. And it is almost always a fluid and sodium problem, not a fitness one.

Terrain and pace change when and how much you eat

Climbing and technical terrain slow you down, which means more hours on course and more total fuel, but they also pull blood away from your gut on the hard efforts. So time your bigger intakes for the runnable and downhill sections where your stomach can handle it, and just sip and nibble on the steep climbs. A slower effort can take on more real food, a faster one leans on liquids and gels.

Build the plan around a realistic finish time for the actual course, not a flat-ground best case. Pacing it by effort and grade keeps your gut online. See how to pace by effort and power-hiking in the pacing guide below.

The overnight shift in a 100 miler

At night your appetite for sweet falls apart and your core cools off, so the plan goes savory and warm: broth, soup, quesadilla, mashed or boiled potato, salty snacks. Your carb intake usually drifts from the daytime 60 to 90 g/hr down toward 40 to 60, and that is fine, your gut just handles less over time. Late in the race the goal is to keep ANY calories going, not to hit a perfect number.

This is where caffeine earns its keep, 50 to 100 mg every couple of hours through the low point, and where eating small and often (every 20 to 30 minutes) beats holding out for one big meal. If your stomach fully shuts down, drop to liquid carbs (cola, broth) and 20 to 30 g/hr just to keep moving.

Rehearse the plan: gut training and long runs

A fueling plan you have never tested is just a guess. The good news is your gut is trainable, the same as your legs.

Train your gut, then nothing is new on race day

Treat long runs like full dress rehearsals: carry and eat the exact foods, gels, and drink mix you plan to race on, at your target grams per hour, in conditions as close to race day as you can get, heat included. Studies show that nudging intake up over a few weeks, starting near 60 g/hr and building toward 90, really does raise your tolerance and cut down on stomach problems, sometimes in as little as two weeks.

Practice eating while climbing and while tired, not just fresh and flat. Note what sat well, what turned your stomach, and when you got sick of the taste, then swap things out and adjust the numbers. By race day, your fueling plan should feel like a habit you have already lived through.

⏵ Stop guessing from a static chart

A generic table does not know your weight, your sweat, your goal time, or the heat and vert of your course. Summit Line builds a fueling schedule, a finish projection, and a pacing plan dialed to YOUR fitness and your exact race, then tracks how your gut and legs handle the load on every long run, so race day is rehearsed instead of guessed.

Get started free →See it on a real race

⏵ Build the plan now, free, no signup

Our free ultra fueling calculator turns this whole method into your own hour-by-hour plan. Pair it with the pacing tools to get an honest finish time for your course, so the hours you are fueling for are the real ones.

See all free running tools →

Keep going: related guides

Ultra fueling plan FAQ

How do I build an hour-by-hour ultra fueling plan?

Five steps. First, figure out your finish time so you know how many hours you are actually fueling. Second, set your hourly targets: roughly 60 to 90 grams of carbohydrate, 16 to 32 ounces of fluid, and 300 to 1000 mg of sodium per hour, and bump those up for heat and long days. Third, pick the real foods and products that hit those numbers and sit okay in your gut. Fourth, take that hourly intake and map it onto the real aid stations and your drop bags, so every carry has enough calories and salt to get you to the next stop. Fifth, write it all down hour by hour, then test the whole thing on long runs and tweak it. The plan is a starting point, not a contract. On race day you eat to the plan until your gut tells you otherwise.

How do I set my carb, fluid, and sodium targets per hour?

Start with the standard ranges and make them yours from there. Carbohydrate: 60 to 90 grams per hour, with an untrained gut closer to 60 and a trained gut on a glucose plus fructose blend getting to 90 or more. Fluid: 16 to 32 ounces (about 0.5 to 1.0 liters) per hour, more in the heat and more to thirst, but stay off both ends, dried out and overdrinking. Sodium: roughly 500 to 1000 mg per liter of fluid, which lands around 300 to 1000 mg per hour depending on how much you sweat and how salty your sweat runs. Salt follows your fluid, so when you drink more in the heat you salt more too. The best way to find your own numbers is to test them in training and run a calculator that factors in your weight, your goal time, and the heat you expect.

What real foods are easiest to stomach mid-race (PB&J, potato, banana, broth)?

The ones that hold up are low in fiber, a little salty, and not too sweet. PB&J on white bread or a white tortilla is the classic, easy to chew with a little fat and protein. Salted boiled potatoes are easy on the gut, salty, and warm at night. Bananas are soft fast carbs early on. Broth, miso, or ramen give you sodium, warmth, and a break from sugar in your head, which is why they end up saving people overnight. Salted rice balls, rice cakes, chips, and pretzels fill out the savory side. Keep gels, chews, and drink mix for exact calories early, then mix in more real food as the sweet stuff starts to turn on you. And whatever you plan to eat, you have to have eaten it on long runs first.

How do I map fuel to aid stations and drop bags?

Pull the aid station chart for your race, write down the mileage and the gap to the next station, and guess how long each carry takes at your pace. Then load each carry with enough carbohydrate and sodium to cover those hours at your hourly target, plus a little buffer in case you are slow. A two hour carry at 80 grams per hour means walking out of the aid station with around 160 grams of carbohydrate on you. Stash the hard-to-find stuff (your specific gels, salt caps, a spare headlamp battery, dry socks, caffeine) in drop bags at the stations that allow them, and let on-course food (broth, potatoes, fruit, soda) cover the rest. Write the plan on a little card or on your bottle: at THIS aid station, do THESE things.

How does fueling change overnight in a 100 miler?

Two things happen at night. Your appetite for sweet falls apart and your core cools off, so the plan goes savory and warm. Lean on broth, soup, quesadillas, mashed or boiled potato, and salty snacks instead of gels. Your carb intake usually drifts down from the daytime 60 to 90 grams per hour toward 40 to 60, and that is fine, your gut just tolerates less as the hours stack up. Late in the race the goal is to keep ANY calories going, not to hit a perfect number. This is also where caffeine earns its keep: 50 to 100 mg every couple of hours through the low point keeps you alert and moving. Keep eating small and often, every 20 to 30 minutes, instead of holding out for one big meal.

How do I account for terrain, heat, and pace in the plan?

Heat pushes your fluid and sodium needs way up and drops your gut tolerance, so in hot races you drink and salt more while often eating a bit less, and you practice in that same heat first. Climby, technical terrain slows you down, which means more hours on course and more total fuel, but it also pulls blood away from your gut on the hard climbs, so time your bigger intakes for the runnable or downhill sections where your stomach can handle it. Pace matters too. A slower effort can take on more real food, a faster one leans on liquids and gels. Build the plan around a realistic finish time for the actual course, not a flat-ground best case, and pace by grade so the effort stays sustainable and your gut stays online.

How do I practice and adjust the plan in training?

Treat your long runs like full dress rehearsals. Carry and eat the exact foods, gels, and drink mix you plan to race on, at your target grams per hour, in conditions as close to race day as you can get, heat included. Gut training is real. Start around 60 grams per hour and nudge it up over a few weeks, and most runners can get to 90 grams per hour comfortably and cut down on stomach problems. Note what sat well, what turned your stomach, and when you got sick of the taste, then swap things out and adjust the numbers. Practice eating while climbing and while tired, not just when you are fresh and flat. By race day, none of it should be new.

What does a sample 50K and 100-mile fueling schedule look like?

A 50K (roughly a 4 to 8 hour effort) you can mostly fuel like a long marathon: 60 to 80 grams of carbohydrate per hour, mostly gels and drink mix, with a banana or half a PB&J at aid stations and caffeine in the back half. A 100 miler (roughly 24 to 30 hours, with cutoffs usually around 30 to 36 hours) is a phased plan: front-load 70 to 90 grams per hour while you are fresh, move to solids like PB&J and potatoes through the day, go savory with broth and soup overnight while dropping to 50 to 75 grams per hour, then drop into survival mode in the final hours where you just get any calories in at all. The full hour-by-hour tables for both are up above in this guide.

This guide is for training and planning, and it reflects general sports-nutrition guidance and ultra coaching practice. Fueling is a very individual thing: your own carb, fluid, and sodium numbers depend on your body, your sweat, your gut training, and the conditions. Test everything in training, build up slowly, and talk to a qualified professional before you make any big changes, especially if you have a medical condition.