NAISMITH’S RULE

(AND WHY IT DOESN’T ALWAYS WORK)

In 1892 Scottish mountaineer William W Naismith came up with a method of calculating how long it should take to cover distance in the mountains. His rule allows 12 minutes per kilometre (assuming an average speed of 5kph/3mph and not allowing for breaks) plus 1 minute for every 10m of ascent.

The problem is that this guide doesn’t allow for variations in fitness, terrain, or fatigue. Various modifications have been introduced (Tranter’s Corrections, for instance), most of which tend to extend the length of time mountain journeys take. Some seek to account for terrain, while others aim to factor in individual fitness. But the fact is that the best method is to use your knowledge and experience of your own abilities. If in doubt, particularly as the days get shorter, it’s best to assume it’ll take longer than you think.