About Naismith's Rule
Created in 1892 by Scottish mountaineer William Naismith, this rule provides a reliable baseline for estimating alpine route times. The original formula states: 1 hour per 3 miles (5km) of horizontal travel + 1 hour per 2000 feet (600m) of ascent.
Modern modifications account for descent time (typically 10 minutes per 300m of descent) and fitness/terrain adjustments.
💡 Important Caveats
Naismith's Rule assumes a fit person on moderate terrain. The calculator adjusts for fitness level and terrain difficulty, but weather, altitude, snow conditions, and group size can all dramatically affect actual times. Always add a 20-30% safety margin, especially for technical routes.
What Affects Actual Time?
- Altitude: Reduced oxygen reduces climbing efficiency above 3,000m
- Snow/ice: Adds 50-100% to times on steep terrain
- Group size: Larger groups move slower; factor in rest breaks
- Pack weight: Heavy loads significantly slow ascents
- Weather: Wind, cold, and visibility can cut speeds in half
Common Time Estimates by Peak
- Matterhorn (4478m): 10-14 hours from Hörnli Hut (summit and return)
- Mont Blanc (4808m): 8-12 hours from Goûter Hut (good conditions)
- Aconcagua (6962m): 6-9 hours from Camp 3 to summit (standard route)