What this tool is, and who it is for
Two formulas — Naismith 1892 and Tobler 1993 — together account for most of the variation in human walking speed. This calculator implements both side by side and lets you see which one fits your trip better. You enter the distance, the total ascent and descent, the terrain class and your pack weight, and it returns moving time, rest-adjusted time and an error range you can use to plan conservatively. It does not pretend to be more accurate than the underlying physics, and the limitations panel calls out the conditions it handles badly.
Climbing speed falls roughly 0.5% per kilogram above 5 kg.
Group pace is set by the slowest member plus waiting time.
Includes breaks, pack weight and party size.
Breaks add 0h 51m.
- —Naismith's Rule: 5h 12m (5 km/h flat, 1 h per 600 m ascent).
- —Tobler's hiking function: 4h 38m (slope-dependent speeds of 3.0 km/h climbing and 4.2 km/h descending).
- —Blended estimate: 4h 55m.
Climbing gradient: 8.5° · descending gradient: 8.5°
Pack factor: ×1.02 on climbing time · party factor: ×1.03
Step-by-step user guide
How to operate the calculator in your browser, what to enter, and what to do with the result.
- 01
Enter the route distance in kilometres and the total ascent / descent in metres. These come from a map or a GPS file.
- 02
Pick the terrain class: paved, maintained trail, rough trail, boulder or talus, or trackless.
- 03
Set your pack weight and your personal flat-ground pace if you have measured one — otherwise leave the default.
- 04
Read moving time, total time including breaks, and the error range. The error range is what you should plan against for daylight-limited trips.
- 05
Add a group-size penalty manually: every party member beyond two typically adds 10 percent to total time for waiting and re-grouping.
What the calculator actually does with the numbers you enter
- 01
Naismith's Rule adds one hour per 600 metres of ascent to a flat-ground pace of about 5 km/h, and remains a serviceable first approximation nearly 135 years after publication.
- 02
Tobler's hiking function models speed as a bell-shaped curve against slope, peaking around 5 km/h on gentle descents and falling steeply on steep ground in either direction.
- 03
Terrain multipliers scale the Tobler result: roughly 1.0 for smooth trail, 0.75 for rough or boulder-strewn ground, and 0.55 for trackless terrain or sustained deep vegetation.
- 04
Pack adjustment reduces climbing speed by approximately 1 percent for every 2 kg carried above a 5 kg baseline, drawn from published load-carriage studies.
Published sources behind the formulas
- [1]Naismith's Rule — original formulation and modern assessmentThe Scottish Mountaineering Club · 2024
- [2]Tobler's hiking function and slope-dependent travelSanta Fe Institute / academic literature · 2023
- [3]Mountain navigation and route timing guidanceMountaineering Scotland · 2025
Frequently asked questions
Short, sourced answers to the questions readers send us most often about this calculator.
Does this work with snow?
Not well. Snow, ice and very cold conditions slow movement well beyond what distance and slope predict. As a rough rule, halve the moving time estimate for any leg that involves postholing or kicking steps in soft snow, and use the upper bound of the error range for anything involving daylight limits.
Why is it not matching my GPS?
GPS tracks measure actual movement, including stops, detours, rest breaks and route-finding. The calculator returns moving time. If your recorded track is shorter than the map distance, you probably took a shortcut or skipped a planned detour; if it is longer, you wandered or took extra breaks. The difference between the two is the most useful planning data point you can record.
What about descents on technical terrain?
Tobler peaks on gentle downhills and falls steeply on steep downhills. On steep scree or wet rock, descent speed can drop below uphill speed, which is the opposite of trail behaviour. Use the rough terrain multiplier and add 30 percent on top for any sustained steep descent on unstable ground.
How does pack weight affect time?
The model assumes roughly 1 percent slower climbing for every 2 kg carried above a 5 kg baseline. The effect on flat ground is much smaller, and on descent it can be near zero or even negative. Use the climbing adjustment for long ascent days and ignore it for ridge walking.