Naismith's Rule is a rule of thumb

Rule of thumb

A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...

 that helps in the planning of a walking

Walking

Walking is one of the main gaits of locomotion among legged animals, and is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step...

 or hiking

Hiking

Hiking is an outdoor activity which consists of walking in natural environments, often in mountainous or other scenic terrain. People often hike on hiking trails. It is such a popular activity that there are numerous hiking organizations worldwide. The health benefits of different types of hiking...

 expedition by calculating how long it will take to walk the route, including ascents. The rule was devised by William W. Naismith

William W. Naismith

William Wilson Naismith was a Scottish mountaineer.He was a key founder of the Scottish Mountaineering Club, often regarded as the "father of the club". He served as its first treasurer....

, a Scottish

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 mountaineer

Mountaineer

-Sports:*Mountaineering, the sport, hobby or profession of walking, hiking, trekking and climbing up mountains, also known as alpinism-University athletic teams and mascots:*Appalachian State Mountaineers, the athletic teams of Appalachian State University...

, in 1892. The basic rule is as follows:

Allow 1 hour

Hour

The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...

 for every 3 miles (5 km) forward, plus 1 hour for every 2000 feet (600 metres) of ascent.

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

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 sight-seeing, or for navigational obstacles. For planning expeditions or walks a party leader may use the rule in putting together a route card

Route card

A route card is a document that is used by hillwalkers as an aid to navigation and route planning. The military also use a similar technique for planning night marches and/or patrols.- Core information: The planned route :...

.

Alternatively, the rule can be used to determine the equivalent flat distance of a route. This is achieved by recognising that Naismith's Rule implies an equivalence between distance and climb in time terms: 3 miles (= 15,840 feet) of distance is equivalent in time terms to 2000 feet of climb. That is, 7.92 (= 15840/2000) units of distance are equivalent to 1 unit of climb. For convenience a 8 to 1 rule can be used. So, for example, if a route is 20 km with 1600 metres of climb (as is the case on leg 1 of the Bob Graham Round

Bob Graham Round

The Bob Graham Round is a circuit of 42 fells in the English Lake District, including the peaks of Skiddaw, Helvellyn, Scafell and Scafell Pike...

, Keswick to Threlkeld), the equivalent flat distance of this route is 20+1.6×8 = 32.8 km. Assuming an individual can maintain a speed on the flat of 5 km/h (walking pace), the route will take 6 hours and 34 minutes. The simplicity of this approach is that the time taken can be easily adjusted for an individual's own (chosen) speed on the flat; at 8 km/h (flat speed) the route will take 4 hours and 6 minutes. The rule has been tested on fell running times and found to be reliable .

In practice, the results of Naismith's Rule are usually considered the minimum time necessary to complete a route. Over the years several "corrections" have been formulated in an attempt to make the rule more accurate. The most common correction is to add 25 or 50% to the time found with Naismith's Rule. While this may be more accurate for some people or under certain conditions, it does not explicitly account for any additional variables. The accuracy of some corrections is disputed by some, in particular the speed at which walkers descend a gentle slope.

Other common corrections are:

• When walking on poor terrain, allow 1 hour for every 2.5 miles (4 km) forward, instead of 1 hour per 3 miles.
• On a gentle decline (about 5-12°), subtract 10 minutes per 1000 feet of descent. On a steep decline (over 12°), add 10 minutes per 1000 feet of descent.

Tranter's corrections

Tranter's corrections make adjustments for fitness and fatigue. Fitness is determined by the time it takes to climb 1000 feet over a distance of ½ mile (800 m). Additional adjustments for poor terrain or conditions can be estimated by dropping one or more fitness levels.

Individual fitness in minutes	Time taken in hours estimated using Naismith's Rule
	2	3	4	5	6	7	8	9	10	12	14	16	18	20	22	24
15 (very fit)	1	1.5	2	2.75	3.5	4.5	5.5	6.75	7.75	10	12.5	14.5	17	19.5	22	24
20	1.25	2.25	3.25	4.5	5.5	6.5	7.75	8.75	10	12.5	15	17.5	20	23
25	1.5	3	4.25	5.5	7	8.5	10	11.5	13.25	15	17.5
30	2	3.5	5	6.75	8.5	10.5	12.5	14.5
40	2.75	4.25	5.75	7.5	9.5	11.5			Too much to be attempted
50 (unfit)	3.25	4.75	6.5	8.5

For example, if Naismith's Rule estimates a journey time of 9 hours and your fitness level is 25, you should allow 11.5 hours.