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How the estimate works
- Distance: 1 hour per 5 km (about 3.1 miles).
- Ascent: plus 1 hour per 600 m of climbing (about 1,970 feet).
- Descent (optional): a correction based on Langmuir's refinement of Naismith. Gentle descents subtract 10 minutes per 300 m; steep descents add 10 minutes per 300 m.
- Pace: the result is multiplied by the pace factor you pick.
- Breaks: the minutes you enter are added for each hour of moving time.
A worked example
Take a 14 km circular walk with 800 m of ascent. Plain Naismith gives 2 h 48 min for the distance and 1 h 20 min for the climbing: 4 h 08 min of moving time. With a relaxed pace factor of 1.2 that becomes about 4 h 58 min, and ten minutes of breaks per hour brings the total to roughly 5 h 47 min. Leaving at 08:30, you would expect to finish a little after 14:15, which leaves a comfortable buffer before dark on most days of the year.
Using it to set a turnaround time
On an out-and-back route, look at the total time and the latest finish you are happy with (well before dark, or before the last bus). Your turnaround time is that latest finish minus the time you need to walk back. A rough rule: half the total time, then a bit earlier, because people slow down on the way back when tired.
On a circular route, pick a checkpoint around the halfway mark and a time you must reach it by. If you're late there, take your escape route or retrace your steps.
Limits of any formula
- Naismith assumes reasonable fitness and paths. Scree, bog, boulder fields and scrambling can be much slower than any setting here.
- Groups move at the pace of the slowest member, and larger groups stop more.
- Heat, altitude and fatigue late in the day all slow walkers down.
Check your real times against the estimate on a few walks. After three or four hikes you'll know your own pace factor, and the calculator becomes much more useful.