23km du Mont-Blanc Aid Station Planner
All 6 23km du Mont-Blanc checkpoints pre-loaded. Enter your goal finish time to get estimated arrival times at every aid station.
Full 23km du Mont-Blanc course data: aid stations, cutoffs, course profile
Enter a goal 23km du Mont-Blanc finish time and get estimated arrival times at every checkpoint - 23 km with around 1,680 m of climbing, with crew and drop-bag points flagged.
Turns every arrival into a clock time and every cutoff into a margin.
Terrain changes how the goal time is shared between segments, not the total. One surface everywhere cancels out.
Checkpoints (6)
Cutoff Sat 10:20
Cutoff Sat 12:20
Cutoff Sat 13:50
23km du Mont-Blanc
Goal 4:31 · Start Sat 07:00
- Crew may meet you at
- Montroc 11.7 km, by Sat 08:57
- La Flegere 19.1 km, by Sat 10:44
- Drop bags
The organiser publishes no drop-bag service anywhere on this course.
| Checkpoint | Dist (km) | D+ (m) | Km-effort | Arrive by | Clock | Cutoff | Buffer | Leave by | Seg time | Seg pace/km |
|---|---|---|---|---|---|---|---|---|---|---|
| Start | 0 | 0 | - | 0:00:00 | Sat 07:00 | - | - | - | - | - |
| Le Lavancher | 5.3 | +202 | 7.5 | 0:47:07 | Sat 07:47 | - | - | Sat 09:09Set by Montroc | 0:47:07 | 8:58 |
| Montroc | 11.7 | +376 | 11.3 | 1:57:57 | Sat 08:57 | Sat 10:20 | 1h22 | Sat 10:33Set by La Flegere | 1:10:50 | 10:57 |
| Bas du Plagnoletlikely hiking (pace) | 15.4 | +345 | 8.4 | 2:50:53 | Sat 09:50 | - | - | Sat 11:26Set by La Flegere | 0:52:56 | 14:32 |
| La Flegerelikely hiking (pace) | 19.1 | +472 | 8.5 | 3:44:30 | Sat 10:44 | Sat 12:20 | 1h36 | Sat 13:03Set by Planpraz (Finish) | 0:53:37 | 14:34 |
| Planpraz (Finish) | 23.0 | +285 | 7.4 | 4:31:00 | Sat 11:31 | Sat 13:50 | 2h19 | - | 0:46:30 | 11:46 |
Le Lavancher
Sat 07:47Leave by Sat 09:09Set by Montroc
- Dist (km)
- 5.3
- D+ (m)
- +202
- Seg time
- 0:47:07
- Seg pace/km
- 8:58
Montroc
Sat 08:57Cutoff Sat 10:201h22
Leave by Sat 10:33Set by La Flegere
- Dist (km)
- 11.7
- D+ (m)
- +376
- Seg time
- 1:10:50
- Seg pace/km
- 10:57
Bas du Plagnoletlikely hiking (pace)
Sat 09:50Leave by Sat 11:26Set by La Flegere
- Dist (km)
- 15.4
- D+ (m)
- +345
- Seg time
- 0:52:56
- Seg pace/km
- 14:32
La Flegerelikely hiking (pace)
Sat 10:44Cutoff Sat 12:201h36
Leave by Sat 13:03Set by Planpraz (Finish)
- Dist (km)
- 19.1
- D+ (m)
- +472
- Seg time
- 0:53:37
- Seg pace/km
- 14:34
Planpraz (Finish)
Sat 11:31Cutoff Sat 13:502h19
- Dist (km)
- 23.0
- D+ (m)
- +285
- Seg time
- 0:46:30
- Seg pace/km
- 11:46
Highlighted rows use a pace heuristic (>12 min/km / >19 min/mi) - likely hiking by speed, not grade. The grade-based power-hike cue is ≥15% (see GAP and Incline tools). Times are distributed proportionally by km-effort.
Leave by is the latest you can start the next segment and still make every cutoff ahead of you at this pace - often set by a station further on, not this one. It does not yet subtract the time you spend stopped, so treat it as the optimistic edge.
Cutoff buffers are estimates from your goal time and published barriers. Courses and barriers change - verify against the official race guide.
Next step
About 23km du Mont-Blanc
23km du Mont-Blanc covers 23 km with around 1,680 m of elevation gain, starting in Chamonix, France. The overall cutoff is 6 hours 50 minutes.
Crew access is allowed at Montroc (11.73 km) and La Flegere (19.05 km).
Checkpoint data approximate - verify against the current official race guide at marathonmontblanc.fr before your race.
The science behind km-effort pacing
Most runners build race pacing plans by dividing total distance evenly - which ignores the fact that an uphill kilometre takes far longer than a flat one. This planner uses TrailMath's enhanced km-effort model to distribute your goal time proportionally by effort, not by distance.
The km-effort formula for each segment is: distance_km + gain_m/100 + loss_m/200. This is TrailMath's extension of the standard ITRA gain-only formula (model TM1, where the descent divisor is a published convention), which adds descent cost because steep technical descents carry real eccentric load. A 5km segment with 500m of gain and 200m of loss has an effort of 5 + 5 + 1 = 11 effort-km - equivalent to running 11km flat. Time is allocated proportionally to this effort score.
Why gain and loss have asymmetric costs. Minetti et al. (2002) mapped the metabolic cost of inclined locomotion across gradients from -45% to +45%. The key findings: metabolic cost rises steeply above 15-20% uphill grade, making power hiking more energy-efficient than running on steep climbs. On descents, eccentric muscle loading (quads acting as brakes) creates its own metabolic cost - steep technical descents are far more demanding than the same gradient on a smooth fire road. The gain/100 + loss/200 asymmetry in the formula reflects this - gain is more costly per metre than loss, but loss is not free.
Power hiking threshold is flagged at segments where your computed pace exceeds 12 min/km (19 min/mile). This threshold corresponds to the crossover point where walking biomechanics become more efficient than running on steep uphill terrain. Strategic power hiking on marked segments preserves leg muscle for descents and reduces overall race time compared to running everything.
This km-effort model is the same formula used in TrailMath's training engine for load calculation (following Dan Johnston's asymmetric elevation scoring methodology), ensuring consistency between how your training load is measured and how your race effort is planned.
Minetti AE et al. (2002). Energy cost of walking and running at extreme uphill and downhill slopes. J Appl Physiol. 93(3):1039-46. Minetti AE et al. (1995). Mechanical determinants of gradient walking energetics in man. J Physiol. 481(Pt 1):235-43. ITRA. km-effort formula. International Trail Running Association. itra.run
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