UTMB Mont-Blanc 100M (the 171 km UTMB, not CCC or OCC)
Chamonix, France · August · 100M
- Distance
- 174 km (108 mi)
- One big loop
- Climbing
- 9,700 m (31,820 ft)
- Mountain: 56 m per km (294 ft per mi)
- Overall cutoff
- 46.8 hours
- 25:54 per mi (16:06 per km) average
- Finish rate
- 70%
- of starters in 2026
Why runners love it
- A loop of Mont Blanc through France, Italy and Switzerland: 174 km (108 mi), 9,700 m (31,800 ft) gain.
- Crowds line Chamonix and the mountain villages; live tracking lets family follow every checkpoint.
- Hot food and heated bases at Courmayeur and Champex-Lac, each with one drop bag.
- Clock-time cut-offs are published for 14 checkpoints, so pacing can be planned.
- Passes above 2,500 m (8,200 ft) with views of the Mont Blanc massif.
Watch out for
- Lottery entry needs Running Stones and a 100K or 100M UTMB Index; 479 EUR (about 550 USD) plus fees.
- First cut-off at 22.9 km (14.2 mi) needs 5.4 km (3.4 mi)/h (3.4 mph); about 30% did not finish in 2026.
- One crew person at four to five points only; help outside those zones draws a 1 hour penalty.
- Snow is possible near 2,300 m (7,500 ft); gear checks are strict and missing items can mean disqualification.
- Three 2026 previews give a 17:45 start and 46 h 45 min limit; the race page header differs.
Race
How runners feel about it, how well it is run, and the community around it. Counts for 25% of the overall score.
Toughness for its distance: Extreme
- Runner satisfactionLoved4.4
Finishers praise the course and crowds; entry rules and commercialisation draw criticism. About 70% finished in 2026. · Medium confidence
- OrganizationWell run4.1
Live tracking and gear checks are strong; confusing rules and chaotic crew access at Les Contamines were reported in 2025. · Medium confidence
- Community and vibeWarm4.0
Crowds line the villages and Chamonix, though some runners find the brand and the stones system corporate. · Medium confidence
Support
Aid stations, crew access, drop bags and pacer rules. Counts for 25% of the overall score.
- Aid stationsStandard3.4
About 14 supplied points over 174 km (108 mi), with a longest stretch near 20 km (12 mi); European fare, thin for vegans. · Low confidence
- Crew accessSome points3.0
Four to five assistance points, one person per runner, and a 1 hour penalty for help outside the zones. · High confidence
- Drop bagsSome stations2.8
One bag each at Courmayeur and Champex-Lac only, in a UTMB-supplied bag. · High confidence
- PacersNot allowed1.2
Being accompanied outside marked spectator zones is penalised, so there are no pacers. · High confidence
Course
Course marking, scenery, and how runners rate the trail itself. Counts for 15% of the overall score.
- Course markingClear4.4
No reports of widespread navigation errors in the accounts read; the evidence is thin. · Low confidence
- ScenerySpectacular4.9
A loop through three countries around the Mont Blanc massif, with passes above 2,500 m (8,200 ft). · High confidence
- Trail experienceRunners rave4.5
Runners rave about the course and fans, though terrain is steep and rocky with long descents. · Medium confidence
Course traits, not part of the score
- FootingTechnical2.2
Rocky, steep and slippery sections, with long stretches that are not runnable, mixed with groomed valley paths. · High confidence
- RunnabilityMixed2.5
Long hiking climbs and steep descents, balanced by runnable valley and village sections. · Medium confidence
- ClimbingMountainous1.0
Climbs 294 ft per mi (56 m per km), from the official elevation gain. · High confidence
Conditions
Race-day temperature and how predictable the weather is. Counts for 14% of the overall score.
- Race-day temperatureWarm or cold3.2
Valley highs near 20 °C (68 °F), cold nights on the passes; 2025 had rain turning to snow near 2,300 m (7,500 ft). · Medium confidence
- Weather reliabilityVariable2.5
Alpine weather swings from heat to snow, extra kit is switched on by forecast, and routes can change. · Medium confidence
Course traits, not part of the score
- AltitudeElevated2.2
High point 2,565 m (8,415 ft), with long time spent above 2,000 m (6,600 ft). · High confidence
Cutoffs
How generous the overall and intermediate cutoffs are for the terrain. Counts for 13% of the overall score.
- Overall cutoffNormal2.9
46 h 45 min for 174 km (108 mi) and 9,700 m (31,800 ft) is about 3.7 km (2.3 mi)/h (2.3 mph); about 30% did not finish in 2026. · Medium confidence
- Intermediate cutoffsTight2.3
Fourteen cut-offs; the first at 22.9 km (14.2 mi) needs 5.4 km (3.4 mi)/h (3.4 mph). Most 2026 dropouts came at Arnouvaz, Courmayeur and La Fouly. · Medium confidence
Intermediate cutoffs (2026)
| Where | Distance | Cutoff |
|---|---|---|
| Saint-Gervais | 23 km (14 mi) | Fri 22:00 (clock time) |
| Les Contamines | 33 km (20 mi) | Sat 00:00 |
| La Balme | 41 km (26 mi) | Sat 02:00 |
| Les Chapieux | 52 km (32 mi) | Sat 05:15 |
| Lac Combal | 70 km (43 mi) | Sat 10:00 |
| Courmayeur | 83 km (52 mi) | Sat 13:15 |
| Arnouvaz | 102 km (63 mi) | Sat 18:15 |
| La Fouly | 116 km (72 mi) | Sat 22:30 |
| Champex-Lac | 131 km (81 mi) | Sun 02:30 |
| Plan de l'Au | 135 km (84 mi) | Sun 03:45 |
| Trient | 147 km (91 mi) | Sun 08:00 |
| Vallorcine | 159 km (98 mi) | Sun 11:15 |
| La Flégère | 170 km (106 mi) | Sun 14:45 |
| Chamonix finish | 177 km (110 mi) | Sun 16:30 |
Not part of the score
- First timer friendlyExperts only1.3
Needs prior Index results at 100K or 100M, plus 174 km (108 mi) of alpine terrain and strict self-sufficiency rules. · High confidence
- Getting inLong-odds lottery1.0
Lottery with Running Stones and a valid 100K or 100M UTMB Index; among the hardest entries in the sport. · High confidence
Stay and travel
Getting there, places to stay, race-day logistics and value. Counts for 8% of the overall score.
- Travel easeFair3.4
Geneva is the usual gateway, then a road transfer; the transfer distance was not checked. · Low confidence
- Places to stayLimited2.3
Race week is very busy in a small valley town, so book far ahead. · Low confidence
- LogisticsSome complexity3.0
One start and finish, but crew bus passes, three countries and bag rules add complexity. · Medium confidence
- ValueFair2.6
479 EUR (about 550 USD) plus fees; strong support and production but the top of the price range. · Medium confidence
Key facts
Checked against the 2026 edition on the official race site. Rules change, so confirm before you enter. Blank means the race does not publish it.
- Location
- Chamonix, Haute-Savoie, France
- Region
- Outside the US
- Typical month
- August
- Latest or next date
- 28 August 2026
- Start time
- 17:45
- First held
- 2003
- Distance
- 174 km (108 mi)
- Course shape
- One big loop
- Surface
- Trail: Alpine trail, rocky paths, some paved and gravel sections through valley towns (France, Italy, Switzerland).
- Footing
- High point 2,565 m (8,415 ft) at Col des Pyramides Calcaires per the official course profile; Col de la Seigne (2,511 m / 8,238 ft) and Grand Col Ferret (2,527 m / 8,291 ft) are the main passes. Reports describe steep, rocky and slippery sections, and long climbs with sustained descents rather than a single peak. The race page warns the distance and gain can be adjusted for terrain.
- Elevation gain
- 9,700 m (31,820 ft)
- Climbing rate
- 56 m per km (294 ft per mi)
- High point
- 2,565 m (8,420 ft)
- Overall cutoff
- 46.8 hours
- Pace to make the cutoff
- 25:54 per mi (16:06 per km)
- Cutoff notes
- Clock-time cut-offs from the official 2026 course data, matched by Cimalp: you must leave each checkpoint by the time shown. The race starts Friday 28 August 2026 at 17:45 and the final cut-off is Sunday 30 August at 16:30, a 46 h 45 min limit (Marathon Handbook and Alps2Alps agree). The race page header shows a 19:45 start and 45 h 30, which does not fit the cut-off table. The first cut-off at 22.9 km (14.2 mi) needs about 5.4 km/h (3.4 mph) from the start. Les Houches, Checrouit and Bertone have no cut-off. Table distances run to 176.9 km (110 mi) at the finish.
- Aid stations
- 14
- Longest gap between aid
- 20 km (12 mi)
- Drop bags
- Some stations
- Crew access
- Some points
- Pacers
- Not allowed
- Support notes
- 14 points with food or drink supplies in the official course data (excluding start and finish); longest stretch between supply points is Les Contamines to Les Chapieux, 19.8 km (12.3 mi), derived from that data (high refuges may offer extra items not listed). Drop bags at Courmayeur and Champex-Lac (UTMB-supplied bag only, no poles inside). Assistance points flagged in the 2026 course data: Les Contamines, Courmayeur, Champex-Lac, Vallorcine and the finish; one person only, handing over a bag up to 30 L (1,830 cu in). A 2025 report used five crew stops. Being accompanied outside marked spectator zones draws time penalties; outside assistance outside zones is a 1 hour penalty. Bring your own cup and bowl (no cups at aid stations).
- Water notes
- Official sources read do not list water crossings.
- Night running
- Two or more nights
- Mandatory gear
- Official regulation: a basic list for all runners plus extra items switched on for the forecast (announced at most 24 h before the start). Missing items draw penalties or disqualification: waterproof jacket with hood, headlamp, survival blanket, smartphone switched on, water reserve. For 2026 one headlamp must have a red setting. Poles, if used, must be carried from the start. Own cup and bowl are expected. Random gear checks on the course.
- Entry
- Lottery + qualifier
- Qualifier needed
- At least 1 Running Stone earned in the last 2 years plus a valid UTMB Index in the 100K or 100M category (registration conditions); each stone is one lottery ticket. Direct entry for elites via UTMB World Series results.
- Entry fee
- About $550
- Fee notes
- About EUR 479.
- Field size
- About 2,407 runners
- Sells out
- n/a (lottery)
- Entry notes
- Fee 479 EUR (about 550 USD at roughly 1.15 USD per EUR) including VAT, plus an 8% administration fee. Pre-registration for 2026 ran in January. A valid UTMB Index in the 100K or 100M category is required; Running Stones are the lottery tickets. field_size is 2026 starters from a French outlet.
- Finish rate
- 70% of starters in 2026
- Air temperature
- 8–20 °C (46–68 °F)
- Weather notes
- Chamonix late August: highs near 20 C (68 F), lows near 8 C (46 F) per Trail Runner; much colder on the passes at night, and a 2025 runner met rain turning to snow near Col du Bonhomme.
- Nearest airport
- GVA (Geneva)
- Stay notes
- Chamonix race week draws very large visitor numbers (Marathon Handbook); book far ahead. Crew need bus passes for some stops (a 2025 runner had to buy them by early July).
- Course record (men)
- 19:37:43 (Jim Walmsley, 2023)
- Course record (women)
- 22:09:31 (Katie Schide, 2024)
Races like this
See every race ranked by likenessClosest on distance, course shape, climbing, footing, region and season.
Kaysville to Midway, UT
Also 100 mi · Point to point or one big loop · Similar footing
Silverton, CO
Also 100 mi · Point to point or one big loop · Same time of year
Easton, WA
Also 100 mi · Point to point or one big loop · Similar footing
Las Palmas de Gran Canaria, Spain
Point to point or one big loop · Similar climbing · Similar footing
What runners and reviewers say
- Educated GuessworkRaced 2022 · blog · Positive
Finished in 37:49:49 (623rd of 1,789) after getting in through the lottery on a later attempt. Terrain was rocky, steep and slippery, hot and humid in the afternoon, and parts were not runnable. Long aid stops (about 1 h 40 min total), a drop bag mix-up and nausea cost time. Crowds and production values were praised; rules and logistics were called confusing.
“not really runnable at all”
- Team RunRunRaced 2025 · blog · Positive
Third UTMB, finished 29:55:38 (170th of 1,665). Rain on the Col du Bonhomme climb turned to wind and snow around 2 a.m. and he was underdressed. Euro-style aid food gave little for a vegan, so crew-supplied gels mattered; five crew stops, bus passes had to be bought by early July, and Les Contamines crew access was chaotic. Gear is checked strictly.
“the best run race out there”
- iRunFararticle · Positive
Explains the Running Stones lottery: at least one stone from the last two years and a valid UTMB Index, one ticket per stone, group entry using the lowest stone count. Describes thousands of amateurs, a party atmosphere and worldwide live coverage. Written in 2022, rules have since changed.
“Big because the course, the fans, and the competition are amazing.”
- Running Tales (Substack)Raced 2023 · blog · Positive
Westcott calls the race addictive with a friendly crowd and strong atmosphere. The 106 mi (171 km) course brings heat, temperature extremes and self-feeding, and he stresses that London-area training cannot prepare you for alpine climbing. Entry is by lottery, one ballot per stone.
“The buzz, the atmosphere, it's just electric.”
- dasz Substack commentsRaced 2023 · forum · Negative
A runner objects to the stones system and the by UTMB branding, saying friends dropped UTMB races because they want to plan their own seasons. He argues an open qualifying system would work financially too. A critical view of entry, not of the course.
“the alarming monopoly position of UTMB”
Show 4 more
- Reference-trail.frRaced 2026 · article · Mixed
2026 numbers: 2,407 starters, 1,681 finishers (69.84%), 726 DNFs. Timing data show the most dropouts at Arnouvaz (about km 100 / mile 62), then Courmayeur and La Fouly. Some DNFs are runners stopped by time barriers.
- Trail RunnerRaced 2026 · article · Positive
Stats piece: 1,665 of 2,492 finished in 2025 (about 66%). Late-August Chamonix highs near 20 C (68 F), lows near 8 C (46 F), colder on the course at night. Lists the 2026 course as 176.2 km (109.5 mi) with about 9,900 m (32,500 ft) and records of 19:37:43 and 22:09:31.
- Marathon HandbookRaced 2026 · article · Mixed
Race-week preview: a strong elite field, live tracking and broadcast, and local debate about night use of protected ground, supporter caps and the expo. For 2026 one headlamp must have a red setting inside a nature reserve. Visitor numbers are unconfirmed but very large.
- CimalpRaced 2026 · aggregator · Mixed
Publishes the 13 checkpoint cut-offs and required pace from the start: 5.4 km (3.4 mi)/h (3.4 mph) at Saint-Gervais easing to 3.8 km (2.4 mi)/h (2.4 mph) late. Warns that starting too cautiously can end the race on the first night and that the cut-off is the time you leave a checkpoint.
Ran UTMB Mont-Blanc 100M (the 171 km UTMB, not CCC or OCC)? Your notes on the footing, cutoffs and aid stations help the next runner decide.
Sources
Pages we used for facts and ratings.
Training for UTMB Mont-Blanc 100M (the 171 km UTMB, not CCC or OCC)? Moku Coach builds your plan around race day.