How long it really takes to climb 800 metres
Naismith’s rule says one thing, the clock another. How a hike’s estimated time is worked out, why it nearly always falls short and how to correct it.
Naismith’s rule, and why it’s still used
In 1892 a Scottish mountaineer, William W. Naismith, summed up in one line what it took him to get around the hills: one hour for every 5 km on the horizontal, plus one hour for every 600 m of ascent.
For a 12 km route with 800 m of elevation gain, that gives 2 h 24 min of forward progress plus 1 h 20 min of climbing: 3 h 44 min. That’s the number you see as the ‘estimated time’ on almost every platform, give or take minor variations.
It’s still used because it’s simple, it’s transparent and it gets the order of magnitude right. What it isn’t is a prediction of how long it will take you.
The key number
Naismith describes a fit mountaineer, with a light pack, on good ground and with no stops. For a normal weekend outing – with lunch, photos and the odd rocky stretch – the actual time usually ends up 25% to 60% longer than the estimate. Those 3 h 44 turn into 4 h 40, or nearly 6.
What the formula leaves out
Stops
40-60 MINNaismith measures movement. Eating, putting on a fleece, checking the map, waiting for the group and taking photos don’t feature in any variable. On a five-hour route it’s normal to clock up 40 to 60 minutes of stops without any single one feeling long.
Descents, which don’t always save time
10 MIN / 300 MThe original formula ignores descent, as if going down were free. Langmuir’s correction and later tables adjust it like this: a gentle downhill speeds you up, but a steep one slows you down – typically you take off 10 minutes for every 300 m of moderate descent, and add 10 for every 300 m of very steep descent, which is where your knees call the shots.
Terrain
UP TO DOUBLEA kilometre of forest track and a kilometre of scree aren’t the same kilometre. Soft snow, mud, boulder fields or tree roots can double the time a section takes without changing either the distance or the climb – which are the only two things the formula knows about.
Fitness and your rucksack
20% OF BODY WEIGHTNaismith’s base pace is the equivalent of walking at 5 km/h on the flat, which is quick with a pack on. And every extra kilo comes at a price: above 20% of your body weight your pace drops noticeably. It’s the variable people planning from the sofa underestimate most.
Altitude
FROM 2,500 MAbove about 2,500 m, performance drops even if you’re perfectly acclimatised. No version of the formula accounts for it, and in the Pyrenees or the Sierra Nevada that means real minutes.
How to correct it, in practice
- 01Work out the Naismith time as a baseline: distance ÷ 5 + ascent ÷ 600, in hours.
- 02Add a third if you’re carrying a normal day pack and walking in a small group. Add half if the group is bigger than four: you move at the pace of the slowest, not the average.
- 03Add stops separately, and count them properly. Ten minutes per hour of walking is an honest figure.
- 04Add another 20% if there’s snow, mud, long stretches of scree or a very steep descent.
- 05Compare with the actual time of someone who’s already done it. It’s the only figure that includes all of the above without you having to estimate it.
Why Suviard shows both
On every route page you’ll see the estimated time and the actual time side by side. The estimate comes from Naismith with its corrections for elevation; the actual time is how long the person who recorded the track took, with their fitness, their gear and whatever the ground was like that day.
Showing only the estimate would look neater and be a lot less useful: a number worked out from two variables can’t know there was half a metre of snow that day. And showing only the actual time doesn’t work either, because it’s one particular person’s. Together they give you the range, which is what you really need to decide what time to set off.
One thing to watch: the actual time depends on the recorded elevation gain, and that figure has its own margin of error. We explain why in why your GPS says you climbed more than you did.
In short
Naismith is a good first approximation and a bad return time. Treat it as the bottom of the range, not the forecast – and remember that any time you think you have to spare on paper is exactly the time you’ll be short of if the ground turns out worse than you expected. The mountains don’t forgive an optimistic figure.
More on how we work with data: about Suviard.