Naismith's rule

Naismith's rule is a rule of thumb that helps in the planning of a walking or hiking expedition by calculating how long it will take to walk the route, including the extra time taken when walking uphill. It was devised by William W. Naismith, a Scottish mountaineer, in 1892. A modern version of this rule can be formulated i.e. as follows:

Allow 1 hour for every 3 mi (5 km) forward, plus 1 hour for every 2000 ft (600 m) of ascent.

The original Naismith's rule from the year 1892 says, that men should allow 1 hour per 3 miles on the map and an additional 1 hour per 2000 feet of ascent. It is included in one, last sentence of his report from a trip. William W. Naismith was a Scottish mountaineer.

Today it is formulated in many ways. Naismith's 1 h / 3 mi + 1 h / 2000 ft can be replaced by:

The basic rule assumes hikers of reasonable fitness, on typical terrain, under normal conditions. It does not account for delays, such as extended breaks for rest or sightseeing, or for navigational obstacles. For planning expeditions a team leader may use Naismith's rule in putting together a route card.

It is possible to apply adjustments or "corrections" for more challenging terrain, although it cannot be used for scrambling routes. In the grading system used in North America, Naismith's rule applies only to hikes rated Class 1 on the Yosemite Decimal System, and not to Class 2 or higher.

In practice, the results of Naismith's rule are usually considered the minimum time necessary to complete a route.

When walking in groups, calculate for the speed of the slowest person.

Naismith's rule appears in UK statute law (although not by name). The Adventure Activities Licensing Regulations apply to providers of various activities including "trekking", and part of the definition of trekking is that it is over terrain from which it would take more than 30 minutes to reach a road or refuge (by the quickest safe route) based on a walking speed of 5 kilometres per hour plus an additional one minute for every 10 metres of ascent.

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