UTMB fuel plan: carbs, fluid and sodium per hour.
Usually in August, Chamonix, France. Set your finish time and the plan follows.
- Distance
- 174 km
- Climbing
- 9,700 m
- Typical temperature
- 9 to 23 °C · 48 to 73 °F
- Aid stations
- 14
Your plan
100 mile · 28 h
Carbs an hour
75g
The research range for this race is 60 to 90 g; your gut training sets where you start. Above 60 g, use glucose and fructose, about 2:1.
Jeukendrup 2014Viribay 2020+4 moreFluid an hour
To thirst
Without a sweat rate the research says drink to thirst. Do the sweat test to get a range.
NATA 2017ACSM 2007Sodium an hour
300 to 1,000mg
Sweat sodium varies a lot between people. A sweat sodium test gives you your own number.
Baker 2017NATA 2017+1 moreAbout 2100 g of carbs over the race. That is a 25 g gel every 20 minutes, or the same carbs from drink and chews.
Rehearse it in training first: the gut adapts in 2 to 4 weeks. Costa 2017
Plan what to carry between aid stations →
Hand it to your AI
Your AI can check these numbers against your training and adjust them. The prompt has your results filled in.
See the prompt
I'm racing a 100 mile and expect to finish in 28 h. I haven't measured my sweat rate. Conditions look mild, and my gut is in some training for fueling. A race fuel calculator built on the research (Jeukendrup 2014, the ACSM 2016 position stand) gave me: 75 g carbs an hour (glucose and fructose, about 2:1), about 2100 g in total; fluid: drink to thirst, no sweat rate yet; 300 to 1,000 mg sodium an hour. Check this against my training and how my gut has handled fueling, then build my race day plan: what to take and when, with real products I can buy.
Gemini, Grok Bot, Dots, Muse and Cue: copy the prompt and paste it in.
With Memory.fit, your AI would already know your sweat rate.
On Android now: get it on Google Play. One email when the iPhone app is on the App Store.
The course
What to know about UTMB.
A loop around Mont Blanc through France, Italy and Switzerland that starts and finishes in Chamonix. The course may be adjusted depending on terrain.
On course: Näak products at most aid stations. Train with what the course hands out, or carry your own.
| Km | Leg | What's there |
|---|---|---|
| 9.1 | run | Les Houches, liquid only |
| 22.9 | run | Saint-Gervais, solid and liquid |
| 32.5 | run | Les Contamines, solid and liquid |
| 52.3 | run | Les Chapieux, solid and liquid, warm meal |
| 69.5 | run | Lac Combal, solid and liquid |
| 78.5 | run | Checrouit Maison Vieille, liquid only |
| 83.3 | run | Courmayeur Sport Center, solid and liquid, warm meal |
| 88.8 | run | Refuge Bertone, liquid only |
| 101.8 | run | Arnouvaz, solid and liquid |
| 116.3 | run | La Fouly, solid and liquid |
| 130.5 | run | Champex-Lac, solid and liquid, warm meal |
| 147.1 | run | Trient, solid and liquid |
| 158.5 | run | Vallorcine, solid and liquid |
| 169.9 | run | La Flégère, liquid only |
Race details checked October 17, 2026 from montblanc.utmb.world, en.wikipedia.org. Courses and aid stations change: check the official page in race week.
Train for it
Train for UTMB with your AI.
With Memory.fit, your AI reads your real training, sleep and fuel, plans your weeks toward race day and shows the plan in the app.
Questions
UTMB: questions.
At a typical finish of 28 h, the research range is 60 to 90 g an hour, as glucose and fructose, set by how trained your gut is. Enter your own finish time above for your number.
Average daily low and high in Chamonix in August (Meteo France 1981 to 2010 normals, via Wikipedia). High passes are much colder, and the race runs through the night. run from about 9 to 23 °C (48 to 73 °F). Heat raises your sweat rate, so do a sweat test in similar weather.
The organizer lists 14 aid stations; the table on this page has each one by km. Check the athlete guide in race week, as positions can change.
Not medical advice. Memory.fit is not affiliated with UTMB or its organizer.
Your next chapter starts with everything you've learned.
On Android now. iPhone is coming: join the waitlist and we'll email you the day Memory.fit is on the App Store.
No spam. One email when it's ready.