Walking-time calculator
Naismith's rule with Langmuir descent corrections, adjusted for terrain, pack weight, fitness and breaks. Enter your route's distance and ascent to get a realistic time estimate with a full breakdown of where the minutes go.
How the estimate works
Naismith's rule (1892) allows one hour for every 5 km of distance plus one hour for every 600 m of ascent. It remains the standard starting point for UK mountain route planning, but it assumes a fit walker on good ground. This calculator layers on the corrections used in mountain-leadership training:
- Langmuir's corrections — moderate descents save a little time; sustained steep descents (over about 12°) cost time instead.
- Terrain factors — rough, boggy or bouldery ground slows every kilometre; winter conditions slow it dramatically.
- Pack weight — around 2% extra time per kilogram above a 5 kg day pack, consistent with military load-carriage research.
- Tranter-style fatigue — beyond five hours' moving, each further hour costs extra, reflecting Tranter's fatigue tables.
These are planning estimates for typical conditions. Navigation difficulty, weather, group pace, and short winter days can all extend a walk well beyond any formula. Plan margins, carry a headtorch, and turn back when conditions demand it.