Why ultras are an eating contest
The running part of an ultra is, oddly, the manageable part. The intensity is low enough that a trained runner can hold the effort more or less indefinitely, which is exactly why the race is won and lost somewhere else: in the stomach. Whether you can keep absorbing carbohydrate, fluid, and sodium for 6, 12, or 24 hours straight decides who finishes strong, who death-marches the last quarter, and who ends up wrapped in a blanket at an aid station. Old ultra hands call these races eating contests with some running attached, and they are only half joking. This planner exists because vague intentions to "eat at the aid stations" do not survive hour ten. Concrete numbers, written down in advance, do.
Setting your three numbers
Carbs first. Ultra intensity sits well below marathon intensity, which means more blood is available to the gut and fat covers a larger share of the work, so 45 to 75 grams per hour works for most runners over most ultra distances. The 90-plus figures you see from elite marathoners belong to shorter, harder races and deliberately trained guts; go higher than 75 only if you have built up to it over months of long training days. Just as important as the number is the menu: variety beats gels-only deep into a race, because a flavor that was fine at hour two can become genuinely repulsive by hour nine.
Fluid next. Somewhere between 0.4 and 0.8 liters per hour is typical, scaling with heat, humidity, and body size. Do not guess when you can measure: weigh yourself before and after long runs with the sweat rate calculator and base your number on your own losses, then adjust on race day for conditions. Drinking far beyond your sweat rate is not extra credit; it just sloshes, and in extreme cases it is dangerous.
Sodium last. A concentration of 300 to 1000 mg per liter of fluid covers nearly everyone, with salty sweaters, the white-crusted-hat crowd, living at the top of that range. The planner multiplies your concentration by your fluid rate, so your hourly sodium automatically rises on hot days when you drink more, which is exactly when you need it. If you have a medical condition that involves sodium or fluid balance, clear your plan with a doctor; this tool is planning math, not medical advice.
Worked example: a 10 hour fueling plan
Take a 10 hour goal at 70 grams of carbohydrate per hour, 0.5 liters of fluid per hour, and 500 mg of sodium per liter. The totals are 700 grams of carbs, which is about 28 gels if you fueled on gels alone, which nobody should; 5 liters or 169 oz of fluid; and 2,500 mg of sodium at 250 mg per hour. Seeing the totals is the point: 700 grams of carbohydrate is a grocery bag of food, and it does not get eaten by accident. It gets eaten because every hour has a line item and you check the lines off.
Making the plan survive the race
A plan that lives in your head dies around hour eight, when race brain sets in. Use the Copy plan button and put the checklist somewhere physical: taped to a flask, printed for your crew, written on the drop-bag list. Tie intake to structure rather than willpower, so the trigger is every lap, every aid station, or a repeating 30 minute watch alarm, never "when I feel like it," because by the time you feel like it you are behind. Decide in advance what the downgrade path looks like when the stomach turns: liquids and simple sugars such as cola, broth, and sports drink keep the numbers alive when solid food will not go down. And rehearse the whole thing, carbs, fluid, and sodium together, on your biggest training days, because race day is a terrible time to discover that your stomach and your spreadsheet disagree.
Related tools and guides
The carb intake calculator goes deep on the per-hour carb science and gut training that sit behind this planner. Estimate how long you will actually be out there with the time on feet calculator, and measure your personal fluid losses with the sweat rate calculator. Racing loops instead of point to point? The backyard ultra calculator handles yard pacing, and training for a backyard ultra with a job and kids covers fitting the preparation into real life.
Frequently asked questions
What if I cannot eat late in a race?
Almost every ultrarunner hits a stretch where solid food becomes impossible. The fix is to downgrade, not to stop: switch to sports drink, cola, broth, or diluted gels, which keep carbs and sodium moving in with almost no chewing or digesting required. Walking for a few minutes while you sip often settles the stomach enough to resume the plan. The runners who quit fueling entirely when the stomach turns are the ones who end up in a chair at the next aid station.
Is real food better than gels in an ultra?
Neither is better; the winning strategy is variety. Gels are dense and easy to count, but ten hours of sweet gels leads to flavor fatigue and a rebellious stomach. Rice balls, potatoes with salt, quesadillas, dates, and broth all deliver usable carbohydrate at ultra intensity, where the gut has more blood flow to work with than in a marathon. Count the carbs in whatever you eat and mix textures and flavors so nothing becomes unbearable at hour eight.
Do I need sodium pills?
Not necessarily. If your drink mix already carries 300 to 1000 mg of sodium per liter, you may be covered by fluid alone, which is exactly what this planner calculates. Capsules are useful when you drink plain water, when it is hot and your sweat is visibly salty, or when you want to adjust sodium independently of fluid. Whatever the source, test it in training. This is general guidance, not medical advice; runners with blood pressure or kidney conditions should talk to a doctor first.
How do aid stations fit into the plan?
Treat aid stations as restock points, not as your fueling schedule. Divide the course by the aid station spacing, work out how many hours each leg takes, and carry that many hours of carbs, fluid, and sodium out of each stop. Grabbing extras at the table is a bonus on top of the plan, not a replacement for it, because station spacing rarely matches a tidy hourly rhythm.
Should I fuel differently at night?
Keep the hourly targets the same but expect the execution to get harder. Appetite fades overnight, cool air masks thirst, and sleepy brains forget to eat, which is why so many races unravel between midnight and dawn. Set a repeating timer, lean on warm options like broth and soup that go down easier in the cold, and have your crew or pacer confirm every feed. Caffeine has its place at night, but it rides on top of the carb plan rather than replacing it.
How do I train my gut to handle this much?
The gut adapts to fueling the way legs adapt to mileage. Start near the bottom of your range on long training days, add 10 to 15 grams per hour every few weeks, and practice with the exact products and foods you will use on race day. Rehearse the full plan, including the fluid and sodium, on at least two or three long efforts before the race. The carb intake calculator covers hourly carb targets and gut training in detail.