How Long Will the Walk Take? Naismith's Rule Explained

Nothing spoils an afternoon like discovering that a walk is going to take twice as long as you thought. Fortunately there is a very old and very simple way to estimate how long a route will take. It is called Naismith's rule, after a Scottish mountaineer, and it has been helping walkers plan their days for well over a century.

The rule itself

The original rule allowed one hour for every three miles walked, plus one hour for every two thousand feet climbed. In metric terms, which is how most of us now work, it becomes:

• One hour for every five kilometres of distance on the map
• Plus one hour for every six hundred metres of ascent

That means a half hour for every three hundred metres of climbing. The rule does not include rests, so you need to add those separately.

A worked example

Suppose a route is twelve kilometres long and climbs a total of six hundred metres.

1. Distance: 12 ÷ 5 = 2.4 hours
2. Ascent: 600 ÷ 600 = 1 hour
3. Total moving time: 2.4 + 1 = 3.4 hours, which is about three hours and twenty-four minutes

Add a lunch stop and a few photo breaks, and it becomes a four-hour outing at a steady pace.

Where to find the numbers

The distance comes from the map. On an Ordnance Survey Explorer map, each grid square is one kilometre across, so counting squares along the path gives a decent estimate. Remember that paths wiggle, so a straight line will underestimate the real length.

Total ascent comes from the contours. Add up all the climbing, not just the difference between the start and the highest point. A route that goes up and down several times can involve far more climbing than the difference between low and high suggests. If this is new, our guide on how to read an OS map explains contour lines.

When to adjust the figures

Naismith's rule describes a fit walker moving steadily on reasonable ground with a light pack. Real life is different, so adjust for:

• Rough, boggy or rocky ground, which slows everyone down
• Heavy rucksacks, including camping gear or young children's belongings
• Steep descents, which can be slow on loose or slippery surfaces
• Poor weather, wind and low visibility
• Fatigue towards the end of the day
• Group size and ability, since the slowest person sets the pace

Many walkers find the rule too fast for them and add a margin of twenty or thirty percent. The best approach is to try it on a few walks, compare it with your actual times and learn your own pace factor.

Add time for stops

Breaks are part of the day. Build in time for lunch, drinks, photographs, wildlife and looking at the view. It is easy to lose forty-five minutes in a morning without noticing. A walk estimated at three and a half hours of moving time might realistically need five hours from door to door.

Using the estimate

Once you have a time, work backwards from sunset and decide on a safe turnaround time. If you have not reached the summit by that time, turn back. This is especially useful in winter, when daylight is short. Our guide on how to plan a day walk shows how this fits into the whole plan.

Keep a record

Write down your planned and actual times for a few walks. After a while you will see how you compare with the rule, and you will plan with more confidence. Over time, you will probably get quicker and stronger as well.

Frequently asked questions

Is Naismith's rule accurate? It is a rough guide, not a precise tool. It works best on typical paths for a reasonably fit walker, and needs adjusting for conditions.

Does the rule include breaks? No. Add your stops separately.

How should I treat very steep descents? They can be slower than flat walking, especially on wet or loose ground, so allow extra time when the map shows steep slopes.