Naismith's rule: the starting point
Formulated by a Scottish mountaineer in 1892, it still underpins almost everything used today. It says to allow 1 hour for every 5 km on the flat, and add 1 hour for every 600 metres of ascent.
A 12 km route with 900 m of gain therefore works out at 2 h 24 min for distance plus 1 h 30 min for the climb: roughly 3 h 54 min of walking. A long way from the three hours in the example above.
Naismith has two known flaws: it assumes a fit walker with a light pack, and it does not penalise descent, even though a very steep descent can be slower than the climb.
The MIDE method
This is the Spanish standard, developed by the FEDME, and you will see it on information boards in many natural parks. MIDE does not just give a time: it scores the route from 1 to 5 across four categories —environment, itinerary, movement and effort— so you know why it is hard, not just how long it lasts.
Its timing is based on reference speeds similar to Naismith's, but it is always expressed as effective walking time: no meals, no photos, no stops. It is an honest figure, but you need to read it correctly.
Draw your route and check distance, elevation gain and estimated time on the map.
Open the GEPYX editorTobler: the refined version
Tobler's hiking function is the most accurate of the three because it computes speed segment by segment as a function of gradient, instead of applying one global average. It has an interesting, counterintuitive consequence: peak walking speed is not reached on perfectly flat ground but on a slightly downhill gradient, around 3 %.
It is the approach that works best on a GPX track, because a GPX file already contains exactly that: the gradient of every small segment of the route.
What no formula knows about you
On top of the theoretical time, always add:
- Stops: lunch, photos, a rest. On a long day that easily adds up to an hour.
- Terrain: scree, soft snow, mud or scrambling can double the time for a section.
- Pack weight: a 12 kg multi-day pack completely changes your climbing pace.
- The group: a group always moves at the pace of its slowest member, and loses extra time regrouping.
- Altitude: above 2,500 m performance drops noticeably.
Work out your own factor
The best method is empirical. Apply Naismith to three or four routes you have already walked and compare against how long you actually took. If you consistently take 20 % longer, that is your factor: apply it every time and your estimates will beat any generic formula.
In GEPYX you get distance and elevation gain as soon as you draw the route, which is all you need to apply any of these methods. And since elevation drives the result, make sure that figure is reliable: we cover it in how elevation gain is calculated.
And the golden rule
Also work out what time it gets dark, and subtract a margin. Most mountain trouble does not come from a route being too hard, but from a route running long and finishing in the dark.
And bear in mind that time is only one of the four dimensions of difficulty: terrain, navigation and the severity of the environment matter just as much, if not more. We cover this in how hiking difficulty is actually measured.