"Are we nearly there yet?"
The classic question from the back seat of a long car journey. Well, when hiking it can often be advantageous to know roughly how long a given walk or section of a route is going to take. How long before you should be able to spot a given feature? Will you make it back before it gets dark? How long will I be exposed to a particular risk? All potential questions that would require you to estimate how much time it will take to cover a certain distance.
So, how do you go about figuring this out? Luckily, a Scottish mountaineer by the name of William Naismith devised a method for doing just that back in 1892 and it's still valid to this day.
Naismith's rule is a means of determining how long it will take you to cover a given route when hiking (without stops). It takes into account the distance to be covered and the total ascent of the route, whilst estimating the speed at which you walk and your speed of ascent.
The original rule worked on the basis of someone travelling at 3 miles per hour then adding on an additional hour for every 2000 feet of ascent. However, in more modern times we have switched from imperial to metric units (at least here in the UK) and so the calculation has been updated to use a speed of 5 kilometres per hour with an additional hour for every 600 metres of ascent, both of which are roughly equal to the original imperial values.
In practical terms this means an estimate of 12 minutes per kilometre plus an additional 1 minute for every 10 metres of ascent.
The calculation can be written out as follows:
time = ((distance ÷ 5) + (ascent ÷ 600)) × 60
Note: Time in minutes, distance in kilometres and ascent in metres.
A route is 8.5km long with 360m of ascent.
((8.5 ÷ 5) + (360 ÷ 600)) x 60
= (1.7 + 0.6) x 60
= 2.3 x 60
= 138 minutes
Answer: 2 hours 18 minutes
Naismith's Rule Calculator
Whether you find the calculation above simple or confusing most of us prefer to take the easy route so below is a Naismith's rule calculator that will perform all of the calculations for you. You can also adjust the pace and speed of ascent values by clicking on settings.
The speed at which you walk can be affected by a number of different factors other than just height gain; conditions under foot, the weather, if you're carrying a heavy pack, etc. As such, with experience you can adjust the formula to fit your abilities and the conditions. Having said all of that, Naismith's rule is still a good general rule and will help give you a rough idea of how long it will take you to get from A to B.