@isazi that would be very useful! Also there’s the German alpine society (DAV) formula where you count like this:
Longitude 1h per each 4km
Ascend 1h per each 300m elevation gain
Descend 1h per each 500m.elevation loss
Add times for elevation gain/loss, compare to the time for longitude: half the smaller of the two and add to the larger of the two.
Example: 15km round tour with 1500m elevation gain/loss.
3h45m for 15km
5h ascend
3h descend
So 3h45m vs 5+3=8h, therefore we half the 3h45m and add it to 8h:
8h+3h45m/2=9h53m
The times are ± realistic, maybe one could set adaptive coefficients for better precision.