What this calculator does
Find out how long your hike will take, so you can plan your start time and get back before dark. A trail's length alone is a poor guide, because climbing is slow. In 1892, the Scottish mountaineer William Naismith suggested a simple rule that walkers still use. Allow an hour for every 5 km (3 miles) of distance. Then add an extra hour for every 600 m (2,000 ft) of climbing (ascent). This calculator applies that rule to your route and shows the arithmetic.
Naismith's rule ignores the downhill parts. The Langmuir option adds corrections from Eric Langmuir's guidance for mountain leaders. Gentle downhill slopes save a little time, and steep ones cost time. You can also change the basic walking speed and the climbing allowance. You can scale the result for a heavy pack or a slower group, and add breaks too.
Where it's used
Why this math matters outside the classroom:
- Day-hike planning. Walkers planning a 15 km route with 900 m of climbing allow 3 hours for distance and 1.5 hours for ascent, about 4.5 hours.
- Outdoor leadership. Expedition leaders split a route into legs and time each one with Naismith's rule to plan checkpoints.
- Daylight checks. Hikers starting a 5-hour route at 1 p.m. in autumn check whether they'll finish before sunset.
- School trips. Teachers use a slower walking speed and a pace adjustment to estimate how long a class will take on a nature trail.
- Rate problems. Students turn 5 km per hour into 12 minutes per kilometer and use it to time a mapped route.
Grade level and standards: Grade 6; Common Core State Standards for Mathematics 6.RP.A.3.b, 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Choose Naismith's rule, or Naismith plus Langmuir's descent corrections.
- Enter the trail distance and the total elevation gain (all the climbing) from a map or route planner. For the Langmuir option, also split the downhill into gentle (5°–12°) and steep (over 12°) sections.
- Keep the classic 5 km/h and 600 m per hour, or change them to match your group.
- Add a pace adjustment and break time if you like. Then read the estimated time and the working.
What the inputs mean
- Total elevation gain
- Add up every climb on the route, not just the height difference between the start and the top. A route that climbs 500 m, drops 200 m and climbs 300 m again has 800 m of gain.
- Gentle descent (5°–12° slopes)
- Downhill parts steep enough to walk easily, but not so steep you have to slow down. That's roughly 5° to 12° (about a 9% to 21% grade). Langmuir takes 10 minutes off for every 300 m of this.
- Steep descent (over 12°)
- Downhill steeper than about 12°, where you slow down to watch your footing. Langmuir adds 10 minutes for every 300 m of this. Very gentle slopes under 5° need no correction.
- Walking speed on the flat
- Naismith's 5 km/h (3 mph) suits fit walkers on good paths. Families, rough ground or big packs may be closer to 3 or 4 km/h.
- Climbing allowance: height gained per extra hour
- How much climbing adds one extra hour. Naismith's 600 m (2,000 ft) per hour is the same as 10 minutes for every 100 m of climbing.
- Pace adjustment
- A percentage applied to the moving time. For example, +20% for heavy loads or a slower group, or −10% for a fast, fit group.
- Breaks
- Total time for rests and lunch.
Formula and method
flat time (min) = distance ÷ walking speed × 60 climbing time (min) = elevation gain ÷ climbing allowance × 60 Langmuir correction (min) = (steep descent − gentle descent) ÷ 300 m × 10 moving time = (flat time + climbing time + correction) × (1 + adjustment ÷ 100) total time = moving time + breaks
Naismith's rule splits a hike into two separate costs: the distance along the ground and the height you climb. Then it adds them together. With the classic figures, every kilometer takes 12 minutes. Every 100 m of climbing adds 10 minutes. The Langmuir correction is optional, and the adjustment is the pace percentage you enter.
Miles and feet are converted with exact factors (1 mi = 1.609344 km, 1 ft = 0.3048 m). The total is rounded to the nearest minute for display.
Worked example
A 12 km round with 800 m of total ascent, at Naismith's standard figures with no adjustment or breaks.
- Flat time: 12 km ÷ 5 km/h × 60 = 144 minutes.
- Climbing time: 800 m ÷ 600 m/h × 60 = 80 minutes.
- Moving time: 144 + 80 = 224 minutes, which is 3 h 44 min.
- With Langmuir corrections for 300 m of gentle and 500 m of steep downhill: (500 − 300) ÷ 300 × 10 = 6.67 minutes more. That gives 230.67 minutes, or 3 h 51 min.
Result: Naismith's rule estimates 3 h 44 min of walking, before any breaks.
Understanding the result
The estimate is moving time for a steady walker on reasonable paths. Add generous breaks. Allow more time for scrambling, snow, bogs or finding your way.
Compare the estimate with the daylight you have. Leave some spare time for delays, rather than planning to finish right at sunset.
Assumptions and limitations
- A steady pace on paths or easy ground, with the speed and climbing allowance you set.
- Elevation gain is the total of all climbs on the route.
- Langmuir's corrections apply only to the downhill you enter for each slope range.
- The rule doesn't model fatigue over long days, altitude, heat or weather.
- Very steep or technical terrain can be much slower than any formula suggests.
- A group moves at the speed of its slowest member. The calculator only captures that through the pace adjustment.
Frequently asked questions
What is Naismith's rule?
It's a rule of thumb for walking time. Allow one hour for every 5 km (3 miles) on the map, plus one hour for every 600 m (2,000 ft) of climbing. William Naismith proposed it in 1892, and it's still taught in hill-walking courses.
Does going downhill really take time?
On gentle slopes you can walk a little faster than on the flat. But steep downhill is slow, because you have to watch your footing. Langmuir's corrections cover both. They take off 10 minutes per 300 m of gentle descent and add 10 minutes per 300 m of steep descent.
Why is my real hiking time different?
Naismith's figures describe a fit walker on good paths. Time yourself on a route you know. Then enter your own speed and climbing allowance, or use the pace adjustment. Future estimates will match you much better.
Should I include breaks?
Yes, for planning a whole day. The rule gives moving time only. Add short rests, photo stops and a longer lunch stop as break time.
How this calculator is checked
Method: Naismith's rule (1892): 1 hour per 5 km plus 1 hour per 600 m ascent; Langmuir's descent corrections (−10 min per 300 m on 5°–12° slopes, +10 min per 300 m over 12°). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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