Will I make the cut-off times?
Check your margin at every intermediate cut-off, not just the one at the finish: it's almost always one of them that knocks you out. That margin is counted in clock time — running plus stops — and the only one that matters is the tightest on the course, never the average.
A cut-off time isn't a performance threshold, it's a schedule. The organizer spreads the time limit along the course knowing the terrain: a steep pass weighs more than rolling ground. That schedule is therefore a progression model already written down, and more reliable than a simple proportion on distance. It is also more selective mid-course than at the end: at UTMB 2025, 82 of the 828 non-finishers were timed out; every one of the others quit before anyone made them.
Three things nibble away at your margin without anyone counting them. Aid station stops first: five minutes per station across fifteen stations costs 1h15, and that stop is modeled separately from movement — 1,667 stops measured at 103 stations across 26 races. Night next, which slows you more than fatigue alone. A start that's too fast, on the other hand, predicts nothing: at comparable level, across the 2,493 starters of UTMB 2025, those who went out fast don't drop out any more often. Below Index 520 the signal even reverses — 58.5% dropped out among the slowest-starting third, versus 28.1% among the fastest-starting third.
On a real race: Mont-Blanc — UTMB®
On Mont-Blanc — UTMB®, a runner with UTMB® Index 600 projects to 37h10, of which 1h54 cumulative stops at aid stations and 20 hours racing at night. These two items don't appear on any pace sheet, and they decide your margin.
| UTMB® Index | Estimated time | Carbs | Fluid | Sodium |
|---|---|---|---|---|
| 500 | 43h01 | 2,581 g | 30.1 L | 21,508 mg |
| 600 | 37h10 | 2,230 g | 26 L | 18,583 mg |
| 800 | 24h36 | 1,476 g | 17.2 L | 12,300 mg |
Temps repris des passages réels des coureurs de chaque tranche de cote sur les éditions précédentes, arrêts aux ravitaillements compris. Besoins calculés à 60 g/h de glucides, 700 mL/h de liquide et 500 mg/h de sodium, par temps tempéré.
Concretely: list every cut-off in the official rules, not just the last two. Compare each to your estimated split time, stops included. Then work backward from your tightest margin — it's the one that matters, and it's rarely the one you feared.
RAVIT applies this calculation to 2,779 races across 49 countries, with 6,547 aid stations whose contents are taken from the official rulebooks.