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Two numbers tell you more about how hard a race actually is than its distance or elevation gain alone: the cut-off times at each checkpoint, and the historical DNF (Did Not Finish) rate. Both are usually published by the organiser, and both are worth reading before you register.
Why cut-offs matter more than the finish-line time limit
Most runners check the overall time limit (say, 30 or 34 hours) and stop there. The intermediate cut-offs at each aid station are the real test — they’re often set tighter in the first half to filter the field and keep later aid stations from being overwhelmed. A generous overall limit can hide a brutally tight early cut-off that ends plenty of races well before halfway.
What DNF rate actually reflects
A high DNF rate isn’t automatically a sign of a badly designed race — it often reflects terrain difficulty, weather variability, or a genuinely tight cut-off structure by design (some races treat a strict cut-off as part of their identity). A low DNF rate can simply mean generous time limits, not that the course is easy. Read DNF rate alongside terrain and elevation, not as a standalone difficulty score.
Where to find the numbers
Look for a “cut-off times” or “règlement / reglamento” (rules) document on the official race site — it usually breaks down the time limit at every checkpoint, not just the finish. Race results archives (often on the organiser’s site or on ITRA’s results database) usually list finisher counts against starters for recent editions, letting you calculate DNF rate yourself if it isn’t published directly.
How to use this when choosing a race
If you’re newer to ultras, favour races with cut-offs that leave real margin over your expected pace — not just your best-case pace. Tight-cut-off races reward experienced runners who pace conservatively early; they’re a poor choice for a first attempt at a new distance.
Found on Ultra Radar Articles — part of our European ultra calendar.