A finishing time on its own tells you very little, since three hours on flat ground and six days unsupported across a mountain range are both recorded as an FKT and nothing on the platform lets you hold one against the other. This tool is one attempt at that comparison.
What it computes
An attempt score is a route difficulty multiplied by three factors,
A = R x S x T x P_rel.
R is the difficulty of the ground, which the tool derives from a GPX file or takes directly if you already have a number from the route difficulty scorer. It combines the kilometer-effort base used in trail running performance modeling [3] with a penalty for sustained steep terrain drawn from the J-shaped cost curve that Minetti and colleagues measured on grades out to 45 percent [1], and
a descent term weighted at roughly half the equivalent climb, following that same work and the grade-by-grade measurements later reported by Jessup and colleagues [2].
S is the style multiplier, at 1.0 for supported, 1.2 for self-supported and 1.5 for unsupported, and T is the team multiplier, at 1.3 for solo, 1.1 for a pair and 1.0 for three or more. P_rel is the previous record divided by your own time, so that taking ten percent off a standing record scores 1.11, while a first run on a new route scores 1.0 because there is nothing yet to measure it against.
What is measured and what is chosen
The difficulty half of this rests on published physiology, the style and team multipliers do not. I am not aware of any study establishing how much harder unsupported is than supported, or solo than a pair, so I picked numbers I can defend and then put them somewhere everyone can see them and change them. If you think 1.5 is too kind to the unsupported runner, say so and give a reason. A parameter you can argue with is worth more than a rule nobody publishes.
What it does not do
It does not rank athletes, it does not know who you are, and it stores nothing: the file you upload is read once and discarded, and no record of the result exists after you close the page. Results are available in metric or imperial. Nothing here is official, and none of it is affiliated with any FKT platform.
What I would like you to do with it
Run one of your own FKTs through it and see whether the number matches what the effort actually felt like.
Bibliography
[1] Minetti, A. E., Moia, C., Roi, G. S., Susta, D., & Ferretti, G. (2002). Energy cost of walking and running at extreme uphill and downhill slopes. Journal of Applied Physiology, 93(3), 1039–1046. https://doi.org/10.1152/japplphysiol.01177.2001
[2] Jessup, L. N., Kelly, L. A., Cresswell, A. G., & Lichtwark, G. A. (2023). It is not just the work you do, but how you do it: the metabolic cost of walking uphill and downhill with varying grades. Journal of Applied Physiology, 135(6), 1263–1267. https://doi.org/10.1152/japplphysiol.00349.2023
[3] Fogliato, R., Oliveira, N. L., and Yurko, R. (2020). TRAP: a predictive framework for trail running assessment of performance. arXiv:2002.01328. https://arxiv.org/abs/2002.01328