Ultra Pacing Calculator

About this calculator

Pacing an ultramarathon is far more complex than pacing a road race because elevation gain, technical terrain, aid-station stops and cumulative fatigue all interact to slow a runner well below their flat-ground pace, and that slowdown compounds as the distance stretches past marathon length. A working ultra-pacing model starts from a known flat pace, adds time penalties for climbing (often modeled similarly to Naismith's rule, which adds fixed time per unit of elevation gain), applies a terrain-difficulty multiplier for trail versus technical singletrack, accounts for planned time at aid stations, and layers on a late-race fade factor to reflect the fact that even well-trained ultrarunners slow disproportionately in the final miles.

Ultrarunners and their coaches use this kind of model to build a mile-by-mile or segment-by-segment pacing plan before a race, to set realistic cutoff-time targets, and to decide how much time buffer to bank early against aid-station cutoffs later in a race. It's also used in reverse — plugging in a goal finish time to see what average pace and effort level is actually required given the course's profile.

This calculator takes your distance, total elevation gain, terrain type, planned aid-station time and flat-ground pace, and returns a projected finish time that accounts for climb, terrain and late-race fade.