Ask a room full of walkers how fast they hike and most will say “about five kilometres an hour”. On a flat towpath with a light pack, that is roughly true. Put the same people on a rocky path that climbs 1,000 m (3,280 ft), add a rucksack, a few photo stops and a lunch, and the honest average drops to something closer to 3 km/h. The gap between the two numbers is the reason so many groups finish in the dark. This article works through the arithmetic, so that a 20 km day on the map becomes a realistic time on the watch.
Flat speed: what the body actually does
Measured over long distances, an adult of average fitness walking on an easy surface settles at 4 to 5 km/h (2.5 to 3 mph). Fit hikers with a purpose can hold 5.5 km/h for hours; a family with children, or a group with heavy packs, is nearer 3.5 km/h. These are moving speeds. The moment you include the pauses that every walk contains, the day-long average is lower again. A useful rule of thumb from mountain leadership training is to budget about 10 minutes of stopping per hour of walking, and more if the group is large, because a group of eight stops far more often than a pair.
Surface matters as much as fitness. Studies of walking economy show that loose scree, deep snow or tussocky bog can double the energy cost per kilometre compared with a firm path, and speed falls to match. The 5 km/h you managed on the forest track is not transferable to the boulder field above the tree line.
Climbing: the rule that has survived since 1892
The oldest and still the most useful formula was proposed by a Scottish mountaineer in the 1890s. In metric terms, Naismith’s rule allows one hour for every 5 km of horizontal distance plus one hour for every 600 m (about 2,000 ft) of ascent. Descent is ignored. The rule is deliberately simple, and it describes a fit walker on a decent path who does not stop.
Apply it to our example. A 20 km route with 1,000 m of ascent gives 4 hours for the distance and 1 hour 40 minutes for the climb, so 5 hours 40 minutes of pure walking. Add the 10 minutes an hour of stops and you are at about 6 hours 40 minutes. Add a proper lunch and the day is around 7 hours. Many hikers who “planned for five hours” have discovered this arithmetic on the hill.
Later refinements have tried to make the rule more honest. One well-known set of corrections deducts 10 minutes for every 300 m of gentle descent, because a slope of 5 to 12 degrees genuinely speeds you up, but adds 10 minutes for every 300 m of steep descent, because anything over 12 degrees slows you down and punishes the knees. Another approach grades the walker by fitness and then multiplies the Naismith time by a factor that grows with the length of the day, which captures the fact that the tenth hour is slower than the first.
A second formula worth knowing
Alpine guides use a slightly different calculation that treats vertical and horizontal effort as one currency. Count one unit for every kilometre of distance and one unit for every 100 m of ascent, then divide by 4 to get hours on the way up. On the descent, divide by 6 instead, because the descent units are cheaper. Our 20 km day with 1,000 m of climbing, split as 10 km up and 10 km down, becomes (10 + 10) / 4 = 5 hours up and (10 + 10) / 6 = about 3 hours 20 minutes down, a total of 8 hours 20 minutes. That is more pessimistic than Naismith, and for an ordinary group with packs it is often nearer the truth.
The two methods bracket reality. When they disagree by an hour, that gap is a measure of how much the day depends on the group.
Vertical speed as a personal number
Many experienced hikers stop thinking in kilometres per hour and think in metres of ascent per hour instead, because on a mountain the climb is what governs the day. A typical figure for a reasonably fit walker with a day pack is 300 to 400 m (1,000 to 1,300 ft) of ascent per hour on a good path. Strong hikers manage 500 m; trained mountain athletes exceed 700 m. A heavy multi-day pack, altitude above 2,500 m, heat, or a technical path with hands-on scrambling can cut the number by a third.
This is a number you can measure. On your next climb, note the altitude at the bottom and the top and the time taken, and you have your own vertical rate. Once you know that you climb at 350 m/h, a col that is 700 m above the car park is a two-hour climb, and no formula is needed.
Load, heat and the second half of the day
Every kilogram in the rucksack costs energy. Physiology research has found that the metabolic cost of walking rises roughly in proportion to the total weight carried, body plus pack, and that the effect steepens once the load exceeds about 20 percent of body weight. In practice, a 15 kg (33 lb) pack on a 70 kg (154 lb) hiker slows a steep climb by 10 to 20 percent, and the effect compounds with fatigue.
Heat is the other silent multiplier. Above 25 C (77 F), sweat losses rise, the heart rate climbs for the same pace, and most groups slow by 10 to 15 percent without noticing. The pace of the first two hours is a poor predictor of hour seven, which is why a plan built on early-morning speed usually fails in the afternoon.
Turning the arithmetic into a plan
The practical outcome of all this is a written timetable rather than a single total. Split the route into legs between obvious features, apply Naismith with corrections to each, and note the expected clock time at each point. Then compare it with the walk as it unfolds. If you reach the first col 30 minutes late, the rest of the day will likely run late by at least the same proportion, and that is the moment to consider the shorter option, not at 4 pm when the ridge is still ahead.
- Flat path, light pack: 4 to 5 km/h moving, 3.5 to 4.5 km/h including stops.
- Ascent: plan on 300 to 400 m per hour, and measure your own rate.
- Steep descent: no faster than the climb, and slower on loose ground.
- Add 10 minutes per hour for stops, plus lunch, plus a margin of 15 to 20 percent for a big day.
A 20 km day with 1,000 m of ascent is, for most people, a seven to eight-hour day. Knowing that before you set off is the difference between a satisfying long walk and a headtorch descent nobody wanted.