How We Calculate
Every number this site produces is an estimate from a published formula. This page sets out each formula, the assumptions inside it, and the conditions under which it stops being reliable. If you want to check our arithmetic, everything you need is here.
Hiking time: Naismith's Rule with corrections
The base estimate comes from Naismith's Rule, published by the Scottish mountaineer William Naismith in 1892. In its original form it allows one hour for every 5 kilometres of horizontal distance, plus one additional hour for every 600 metres of ascent.
Used alone, that rule assumes a fit walker, good conditions, a light load, and no fatigue over the course of the day. We apply two standard modifications:
- A fitness scaling factor, in the manner of Tranter's corrections, which adjusts the base time up or down according to the pace you select.
- A descent adjustment, following Langmuir's amendment: time is subtracted for gentle descents, where gravity assists, and added for steep ones, where careful foot placement makes you slower than on flat ground.
The result is a moving time. It excludes breaks, photographs, navigation stops, and time spent at the summit. For a full day out, most parties should add somewhere between 20 and 40 per cent to the figure the calculator returns.
Energy cost: MET values
Calorie estimates use the Metabolic Equivalent of Task method, drawn from the Compendium of Physical Activities. One MET represents resting metabolic rate. The calculation is:
Calories per hour ≈ MET value × body mass in kilograms
We select a MET value from the grade and the pack load you enter, ranging from roughly 4.5 for easy walking on flat ground to above 9 for steep climbing under a heavy load. Load is applied approximately linearly, following the general finding from load-carriage research that energy cost rises roughly in proportion to carried weight as a fraction of body mass, with the cost rising faster above about 30 per cent of body weight.
This method has known limits. It uses population-average metabolic costs and cannot account for individual efficiency, which varies meaningfully between people of the same size. It does not model heat, altitude, or terrain surface, each of which can raise real energy cost substantially.
What the calculator does not do
- It does not route. You supply distance and elevation gain; the calculator does not know the shape of your route, where the climbing sits within it, or whether a trail exists.
- It does not model surface. Sand, deep snow, talus and blowdowns can raise both time and energy cost by 20 to 60 per cent, and none of that appears in the output.
- It does not model altitude. Above roughly 2,500 metres, performance declines for reasons the formulas do not capture.
- It does not model weather. Heat, cold, wind and visibility all change real times considerably.
- It is not a safety margin. Treat the output as the fastest plausible time for a competent party in good conditions, and plan your turnaround from that with your own margin added.
How accurate is it in practice?
For a maintained trail, in reasonable weather, with a moderate load and an honestly selected fitness level, expect the time estimate to land within roughly 15 to 25 per cent of your actual moving time. Calorie estimates carry wider uncertainty — individual variation and the limits of the MET method mean an error band of 20 to 30 per cent is realistic, which is still better than most wrist-worn devices manage under load.
Both figures degrade sharply on technical ground, in bad conditions, and at altitude. If you are planning close to your limits, plan from experience on similar terrain rather than from any calculator, including this one.
Corrections
If you have walked a route and measured something materially different from what this tool predicted, we want the data. Details are on the contact page, and our approach to corrections is set out in the editorial policy.