Hiking Time Calculator
Naismith’s rule with Tranter’s fitness corrections, Langmuir’s descent rule and honest allowances for your pack, the ground and the group — and a breakdown of how much of the day is the climb.
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What Naismith’s rule actually says
William Naismith, in 1892, wrote down a rule of thumb that has outlived every attempt to replace it: allow one hour for every 5 km of distance, plus one extra hour for every 600 m of ascent. That is the whole rule. It describes a fit hillwalker, on a reasonable path, in reasonable conditions, moving without stopping.
Two things follow from that. The first is that Naismith is a floor, not a forecast — every real-world factor makes it longer, never shorter. The second is that the split between the distance term and the climb term tells you something useful about the day, which is why this page prints it. A 14 km walk with 900 m of ascent is 2 h 48 for the distance and 1 h 30 for the climb: the climb is a third of the day. On a short, steep route the climb can be two thirds, and the distance figure people quote each other in the car park is nearly meaningless.
Tranter’s corrections are the part everyone skips
Philip Tranter published a correction table that takes the Naismith figure and adjusts it for individual fitness and for the length of the day. It is the piece that makes the rule usable by someone who is not a fit Victorian Scot. Fitness is measured with a specific test — how many minutes it takes you to climb 300 m of height over 800 m of distance, at a pace you could sustain. Fifteen minutes is very fit. Fifty is unfit.
The important property of the table is that the penalty compounds with time. At a two-hour Naismith estimate, an unfit walker takes about a third longer. At a ten-hour estimate, the same walker takes nearly twice as long. Fatigue is not linear, and any calculator that multiplies your time by a single fitness factor is getting long days badly wrong.
Tranter also gave two instructions that this page follows: drop one fitness level if you are carrying a heavy load, and drop levels again for bad conditions. We apply the load rule directly and handle conditions through the ground-underfoot factor instead.
Langmuir on descent
Naismith charges nothing for going down, which is wrong in both directions. Eric Langmuir’s correction: subtract 10 minutes per 300 m of descent on gentle slopes, where you can stride out, and add 10 minutes per 300 m on steep ground, where you are braking on every step. Anyone who has come off a scree slope knows which way that goes. Steep descent is also where injuries happen, and where a group spreads out furthest.
What this cannot know
- Altitude. Above roughly 3,000 m the same fitness buys less. If your route spends the day above that, drop a fitness level; above 4,000 m, drop two. The Caucasus 4,000ers punish people who planned them at sea-level pace.
- Snow, heat and wind. Breaking trail through soft snow can halve your speed. So can 35 °C. The ground-underfoot setting covers some of it and nothing covers the rest.
- Navigation. Time spent working out where you are does not appear in any formula. On a marked trail it is nil. Off one, in cloud, it can be a third of the day.
- The turnaround. Estimate the time to the summit separately, and decide before you leave what time you turn around whether you are there or not. Most benightments are a planning failure, not a fitness one.
Where the numbers come from
Naismith’s rule and Langmuir’s descent correction are as published. Tranter’s corrections are the published table, with values between its columns interpolated and values past its right-hand edge extended on the same trend — the original table simply stops, on the grounds that a very long day at low fitness should not be attempted. The ground-underfoot and group-size multipliers are ours, and they are judgement rather than measurement: treat them as a way of being consistent with yourself, not as science.
Questions people ask
Is Naismith’s rule still accurate?
For its stated case — a fit walker, a good path, decent weather, no stops — it is remarkably good, which is why it has survived since 1892. The trouble is that almost nobody is in its stated case. The corrections on this page exist to move the estimate from that ideal walker to you.
Why does my hike take longer than the calculator says?
Usually one of four things: the ascent figure was the summit height minus the car park height rather than cumulative climbing, the distance came off a map rather than the ground, nothing was allowed for stops, or the fitness setting is optimistic. Go back and check the ascent first — it is the most commonly wrong input by a wide margin.
How do I find the total ascent for a route?
From a GPX or a mapping site, and then sanity-check it: raw GPS altitude wanders, so an unsmoothed total can be hundreds of metres too high. Our elevation gain calculator shows you the size of that error on your own data.
Does this work for running or for trekking with a mule?
No. Naismith describes walking. Trail running has its own pacing models, and pack animals change the problem entirely — you move at the animal’s pace on the flat and lose less than you would expect on the climb.
Is anything I type here sent anywhere?
No. There is no backend on this page. The calculation runs in your browser and nothing is uploaded, logged or stored.
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