How pack weight changes your hiking time
A heavier overnight pack slows a climb. Most hiking-time estimates ignore this because they're built on Naismith's rule (1892) — flat pace plus 1 hour per 600 m of ascent — which was written for a light daypack, not a multi-day load. Far scales the ascent portion of the estimate by your real pack weight instead of ignoring it.
The formula
Flat-ground pace is assumed at 4.5 km/h. Ascent time is 1 hour per 600 m of elevation gain, scaled by:
70 kg is a reference adult body weight — used only to express pack weight as a fraction of total mass moved uphill, not a claim about your actual weight. 5 kg is the light daypack load Naismith's original rule is understood to assume. Below 5 kg of pack weight, the multiplier stays at 1 — the estimate doesn't speed up for an already-light kit, only slow down for a heavier one.
Worked example
A 12 km day with 600 m of ascent. Flat-pace time is fixed (12 ÷ 4.5 ≈ 2h 40m); only the ascent portion changes with pack weight.
| Pack weight | Ascent multiplier | Estimated time |
|---|---|---|
| 5 kg (baseline) | 1.00× | 3h 40m |
| 20 kg | 1.20× | 3h 52m |
| 35 kg | 1.40× | 4h 04m |
Modest differences on a single climb compound across a multi-day trip's total ascent — this is why the effect matters more for route planning than for any one segment.
Descent isn't free either
When a route's elevation profile is available, Far costs descent by grade (Langmuir's correction to Naismith): steeper than about −12° slows you down (loose footing, switchbacks) and adds roughly 1 hour per 920 m of that descent; between −12° and −5° a gentle downhill actually aids pace, crediting about 1 hour per 1,800 m; gentler than that is treated as free. Without a per-point profile, Far falls back to a flat rate of 1 hour per 920 m of total descent rather than treating all descent as free time, which older estimates often do.
Limitations
- This is a planning estimate, not a guarantee — fitness, trail surface, weather, and breaks all move the real number.
- 70 kg and 5 kg are stated reference constants, not measurements of you or your gear.
- The estimate never drops below 60% of flat-pace time, even on a very generous downhill — a fast descent is still a hike, not a run.
Formula current as of 2026-07-19. Source: Far's own hiking-time estimator, applied identically in the app.