100K Ultramarathon Nutrition Plan: Carbs, Drop Bags, and Aid-Station Math

A 100K asks you to solve a packing problem the marathon rarely forces and the hundred-miler usually hands to a crew. Aid gaps can stretch past seven miles, sweetness often quits before the finish, and the vest has to carry counted carbs across the long stretches between reliable tables.

It adds hours past a 50K where small fueling misses compound, and you're usually short of a full overnight 100-mile campaign. So the useful 100K ultramarathon nutrition plan is an hourly target you've already practiced, mapped onto the actual athlete guide, with drop-bag resets that match the course you entered.

How many hours of eating is a 100K?

A hundred kilometers is about 62.1 miles. That conversion helps packing, but hours on course drive how much you carry.

A faster runner may finish in the low teens; a first-timer on a mountain course may spend closer to the mid-teens or longer. Those are planning bands, not a claimed average. Use your own training paces and the current course guide for a race-specific number.

Write the day as hours of work. Twelve hours at 55 g of carbohydrate per hour is 660 g of planned carbs. Fifteen hours at the same target is 825 g. Same hourly number, different packing problem. That's why finish-time estimates belong next to the carb target before you start stuffing wrappers into a vest.

And start earlier than hunger, because waiting until food "sounds good" is how you fall behind while you still feel fine.

How many carbs per hour for a 100K?

The short answer: treat about 30–50 g/h as a conservative starting range, then build toward about 50–70 g/h when gut training already supports it.

The ISSN single-stage ultra position stand puts racing intake in a broad 150–400 Kcal/h band, with about 30–50 g/h of carbohydrate and 5–10 g/h of protein from foods you can actually tolerate (Tiller et al.). Fluid guidance in that same stand lands around 450–750 mL/h, with sodium often needed above what many commercial drinks supply (greater than about 575 mg/L).

That ISSN range is deliberately conservative. The 50-mile ultra nutrition plan walks a counted example near 60 g/h for a runner who has already practiced it, and the 100-mile nutrition plan uses about 50–70 g/h for most trained first-timers. A 100K sits between those distances, so the same 50–70 g/h planning band fits a gut-trained target here too.

Field ultras often land short of what blogs promise. Costa and colleagues note many runners take in closer to 20–40 g/h even when they planned higher. Observational trail data in 22 runners found higher finishers took in more carbohydrate, especially early; that study doesn't establish causation (Inamura et al., Scientific Reports). A 2026 Sports Medicine review discusses those associations while stressing that evidence past about 90 g/h remains limited and should stay individualized (Plews, Booth, Krieger, and Maunder).

Situation	Flexible planning band
Sensitive gut or less experienced	About 30–50 g/h
Most trained runners	About 50–70 g/h
Experienced, gut-trained	About 70–85 g/h
Advanced, individually tested	About 85–90+ g/h

These are flexible planning bands, not hard thresholds. Treat anything above about 90 g/h with the caution Plews and colleagues describe: limited evidence, individual testing only.

During-exercise targets are usually absolute grams per hour, not a simple body-weight formula. A smaller runner, including a woman, shouldn't automatically cut the number in half because a chart looked male-heavy. Individualize from training, not from a sex-based discount.

If you want the higher end, earn it with gut training and, when intake climbs, understand why mixed carbs matter in the glucose-to-fructose guide. Don't wait until the start corral to find out whether a new product agrees with your gut.

How do you turn the aid-station chart into carries?

An hourly target does nothing until you pin it to the course.

Pull the current athlete guide first. Write the gap to the next reliable water, food, or drop bag in hours at a late-race pace, not your fresh-legs fantasy. Then multiply for the longest gap, not the average. Plan what you carry around the longest time between aid stations, not the average distance.

Worked Miwok 100K segment

On the Miwok 100k aid-station chart, distance to the next aid ranges from 4.3 to 7.4 miles. Drop bags and crew sit at Tennessee Valley outbound (mile 13.0), Tennessee Valley inbound (mile 26.0), and Randall Trailhead (mile 49.2). The longest listed gap is Bridge View → Tennessee Valley inbound: 7.4 miles.

Illustrative late-race pace for this example: about 14:00 per mile, or roughly 1 hour 45 minutes (1.75 h) for that 7.4-mile segment. At a gut-trained 55 g/h carbohydrate target, 600 mL/h fluid, and sodium coming mostly from drink mix:

Need for the 7.4-mile carry	Math	Leave Bridge View with about
Carbohydrate	1.75 h × 55 g/h = 96.25 g needed	plus a 20–30 g delay buffer → 116–126 g packed; this example packs 123 g
Fluid	1.75 h × 600 mL/h = 1,050 mL	about 710–950 mL of prepared drink (two packets mixed as directed), topped up with plain water to ~1,050 mL
Sodium from mix	two Skratch Orange packets (400 mg sodium each per manufacturer label) covering that fluid	800 mg from drink mix before food salt

One practical vest load for that gap: two Maurten Gel 100 packets (25 g carbohydrate each), two Skratch Labs Sport Hydration Mix Orange packets (20 g carbohydrate and 400 mg sodium each per manufacturer Nutrition Facts label), and Snyder's of Hanover Sourdough Hard Pretzels totaling one 1 oz / 28 g serving (22 g carbohydrate) plus a half serving (~14 g pretzels, 11 g carbohydrate). That is 25 + 25 + 20 + 20 + 22 + 11 = 123 g of carbohydrate, which sits inside the 116–126 g buffer range above. Two packets mixed as directed (12–16 fl oz / about 355–473 mL each) make about 710–950 mL of prepared drink, so top up with plain water to reach ~1,050 mL.

Use the mile-13 and mile-26 Tennessee Valley bags to restock gels, drink-mix packets, and one savory backup before the longer middle gaps. Use the mile-49.2 Randall bag to simplify for the final stretch: easiest tolerated carbs, planned caffeine if you use it, and enough fluid capacity for the remaining ~13 miles of charted trail to the finish. Replace every product assumption with your own labels and the current year guide.

Vest, drop bag, and course table have different jobs:

• Vest: enough counted fuel for the next gap, plus the delay reserve
• Drop bag: your exact gels or drink mix, salt sources, planned caffeine, and one savory backup the course may not stock
• Course table: water, listed sports drink, and optional extras you have already practiced, never the entire strategy

On climbs, station-to-station time beats the mile split for deciding what leaves in the vest.

Need a starting carb, fluid, and sodium timeline before you mark the map? Build one in about 60 seconds with the free EnduranceOS planner.

Sweet early, savory later

Early hours are when measured gels, chews, and drink mix make the bookkeeping less stupid. My default for a first 100K is still that backbone, for the same reason it shows up in the gels vs chews vs drink mix post: it's not rocket appliances, you can just count the grams. Real food can join as support; it shouldn't become "whatever looks good."

Later, sweetness often quits. Potatoes, broth, pretzels, or rice balls can keep calories moving when another gel feels like a dare. The ISSN stand calls out that savory preference in longer races (Tiller et al.). Use it, keep counting, and measure training portions so mile-40 you isn't guessing.

Fluid and sodium without turning the day into a drinking contest

Carb math can't tell you how much to drink. ISSN's racing fluid band of about 450–750 mL/h is a starting range, not a personal prescription (Tiller et al.). Use the sweat-rate guide when you can, then adjust with thirst, heat, and stomach comfort.

Count every fluid in one column, and count sodium across mix, food, broth, and capsules. The sodium-per-hour guide explains why mg/L and mg/h differ. Salt tablets only close a practiced sodium gap; they don't make overdrinking safe. For that risk, see the hyponatremia guide and hot-weather adjustments.

A counted ~13-hour 100K example

Here is an illustrative plan for a runner expecting cool to moderate conditions and roughly thirteen hours on course. This athlete has repeatedly tolerated about 55 g/h of carbohydrate, a fluid range near 600 mL/h, and sodium coming mostly from drink mix plus salty food. These are example numbers, not a prescription for your body, your course, or your weather.

This sample is mainly a carb plan. The ISSN position stand also discusses about 5–10 g/h of protein from tolerated foods (Tiller et al.); the hourly table below doesn't count protein toward that guidance, so if you want that protein band, add it from practiced foods in its own column.

Label assumptions used below:

• Maurten Gel 100: 25 g carbohydrate per sachet (manufacturer FAQ)
• Skratch Labs Sport Hydration Mix, Orange: 20 g carbohydrate and 400 mg sodium per serving mixed in 12–16 fl oz (manufacturer Nutrition Facts label for Orange)
• Snyder's of Hanover Sourdough Hard Pretzels: 22 g carbohydrate and 190 mg sodium per 1 oz / 28 g serving; a half serving is ~14 g pretzels (11 g carbohydrate, about 95 mg sodium); a 10 g-carb training bag is ~13 g pretzels (about 88 mg sodium)
• Homemade rice ball: about 106 g cooked white rice supplies about 30 g carbohydrate, using USDA FoodData Central cooked long-grain white rice at 28.2 g carbohydrate per 100 g (USDA FDC 168878). FoodSafety.gov flags Bacillus cereus risk in cooked rice left too long at room temperature; chill perishable food within 2 hours (within 1 hour above 90°F / 32°C). Keep homemade rice balls cold in an insulated bag with an ice pack, or have crew hold them cold, and don't leave them in an all-day drop bag in the sun. If cold storage isn't realistic, swap that hour for a shelf-stable carb you already practice.

Hourly template (same items, counted grams):

Race hour	Counted items	Carbs	Fluid	Pack notes
0:00–1:00	1 Maurten + 1 Skratch + ~13 g pretzels (10 g carbs)	55 g	~600 mL	Start carry + buffer
1:00–2:00	1 Maurten + 1 Skratch + ~13 g pretzels (10 g carbs)	55 g	~600 mL	Same template
2:00–3:00	1 Maurten + rice ball (~106 g cooked rice, 30 g carbs)	55 g	~600 mL	Real food; bottle may be water-only
3:00–4:00	1 Maurten + 1 Skratch + ~13 g pretzels (10 g carbs)	55 g	~600 mL	Hours 0–4 sum: 220 g
4:00–5:00	1 Maurten + 1 Skratch + ~13 g pretzels (10 g carbs)	55 g	~600 mL	Restock gels/mix at mid-race drop when allowed
5:00–6:00	1 Maurten + rice ball (~106 g cooked rice, 30 g carbs)	55 g	~600 mL	Savory when citrus fades
6:00–7:00	1 Maurten + 1 Skratch + ~13 g pretzels (10 g carbs)	55 g	~600 mL	Keep the measurable base
7:00–8:00	1 Maurten + rice ball (~106 g cooked rice, 30 g carbs)	55 g	~600 mL	Hours 4–8 sum: 220 g
8:00–9:00	1 Maurten + 1 Skratch	45 g	~500–600 mL	Soften a touch under 55 late
9:00–10:00	1 Maurten + rice ball (~106 g cooked rice, 30 g carbs)	55 g	~500–600 mL	Easier chew when gels wear thin
10:00–11:00	1 Maurten + 28 g pretzels (22 g carbs)	47 g	~500–600 mL	Practiced broth OK if logged
11:00–12:00	1 Maurten + 28 g pretzels (22 g carbs)	47 g	~500–600 mL	Practiced caffeine in its own column
12:00–13:00	1 Maurten + 1 Skratch + ~14 g pretzels (11 g carbs)	56 g	~500–600 mL	Hours 8–13: 250 g; day 690 g

Phase totals beneath the table: hours 0–4 = 220 g at 55 g/h; hours 4–8 = 220 g at 55 g/h; hours 8–13 = 250 g at a softer late target; full day = 690 g over 13 hours. That isn't a flat 13 × 55 = 715 g. If you hold 55 g/h all the way through hour 13, the day becomes 715 g instead; write which version you're packing before the start.

Pack for the day (690 g planned consumption)

The 690 g below is planned consumption for the 13-hour template, not your full inventory. Pack emergency or buffer items on top (for example the Miwok segment's extra half-serving pretzel buffer, plus any delay reserve you write for the longest gap).

Product	Count for the 13 h plan	Carbohydrate
Maurten Gel 100	13 sachets	13 × 25 = 325 g
Skratch Sport Hydration Mix (Orange)	7 packets	7 × 20 = 140 g
Snyder's Sourdough Hard Pretzels	five ~13 g bags (10 g carbs each) + two 28 g servings (22 g carbs each) + one ~14 g half serving (11 g carbs)	50 + 22 + 22 + 11 = 105 g
Homemade rice balls (~106 g cooked rice each)	4	4 × 30 = 120 g
Day total		690 g

Sodium accounting from the counted rows (Skratch Orange + Snyder's portions only):

• Skratch: 7 × 400 = 2,800 mg
• Pretzels, scaled from Snyder's 190 mg per 28 g: five ~13 g bags ≈ 5 × 88 = 440 mg, two 28 g servings = 2 × 190 = 380 mg, one ~14 g half serving = 95 mg → 440 + 380 + 95 = 915 mg
• Counted day total: 2,800 + 915 = 3,715 mg over 13 hours ≈ 286 mg/h

Planned fluid from the table is about 7.3–7.8 L (eight hours at ~600 mL plus five late hours at ~500–600 mL each). Across that range, 3,715 mg is about 476–509 mg/L. The ISSN ultra position stand discusses about 500–700 mg/L as an initial sodium guideline during long-duration racing (Tiller et al.). This example's counted Skratch-plus-pretzel sodium sits near the low end of that band before other food sources, and it isn't a personalized replacement target. Plain cooked white rice from USDA FDC 168878 is essentially unsalted (1 mg sodium per 100 g, so about 1 mg in a ~106 g ball). Homemade onigiri sodium depends on the salt you add, so it isn't counted here. Don't add extra salt blindly; close any practiced gap with foods, broth, or capsules you've already tested, using the sodium-per-hour guide and your own sweat-rate data.

Real-food substitution (same hour)

Replace one Maurten (25 g) + one Skratch (20 g) hour (45 g) with:

• 1 rice ball (~30 g from ~106 g cooked white rice) + 28 g pretzels (22 g carbs) = 52 g

Or keep the Skratch bottle for fluid/sodium and swap only the gel for the rice ball when sweetness dies. Rehearse the chew and the pocket.

If you're 45 minutes behind

A 45-minute delay at 55 g/h is about 41 g of extra carbohydrate and about 450 mL of extra fluid before you even talk about a slower pace into the next station. Before you leave the table, add one Maurten (25 g) plus enough drink mix or pretzels to cover the rest, refill to the new time estimate, and skip trying to "catch up" by stacking three gels in ten minutes. Confusion, severe or worsening headache, repeated vomiting, unusual swelling, or loss of coordination are reasons to seek race medical help, not another self-experiment (Hew-Butler et al.). The stomach-problems guide covers the less dramatic causes.

Optional caffeine belongs in its own column (coffee, gels, gum, cola all count). Save most for the back half and rehearse the dose; details are in the caffeine timing guide.

A simple first-100K checklist

For a first 100K, keep the plan tied to the longest gap on your athlete guide:

• Aim near 30–50 g/h until training proves a 50–70 g/h band
• Start fueling in the first 30–45 minutes
• Map every long gap into grams to carry, using the longest gap rather than the average
• Keep fluid and sodium in separate columns from the carb target
• Practice the exact products on long runs, then write the drop-bag jobs while your brain still likes math

Stepping toward a hundred miler? The overnight crew and darkness logistics in the 100-mile plan are the next layer.

The EnduranceOS planner builds an hourly carb, fluid, and sodium plan from your race details in about 60 seconds. It's free. Take it to your course map, count what you swallow in training, and adjust until the numbers survive a long day.

This article is educational, not individual medical advice. Medical conditions affecting nutrition or fluid balance, recurring symptoms, or uncertainty about an appropriate target call for guidance from a qualified clinician or sports dietitian.