# How Long Will This Hike Take, and How Heavy Should My Pack Be?

Naismith's rule is from 1892 and still works, as long as you know what it leaves out. The two corrections worth applying, and what a loaded pack should actually weigh.

---

- **Canonical URL:** https://dothecalculation.com/blog/hobby/hiking-time-and-pack-weight
- **Category:** Hobbies & Leisure Utilities
- **Author:** Do The Calculation Team
- **Published:** 2026-09-20
- **Reading time:** 17 min read
- **Publisher:** Do The Calculation (https://dothecalculation.com)
- **Methodology:** https://dothecalculation.com/methodology

---

Two numbers decide whether a day on the hill is enjoyable or grim: how long it will actually take, and how much you are carrying while it takes that long. Both have well-established estimates behind them, and both estimates are honest about being estimates — which is more than most trail apps manage.

## Naismith's rule

William Naismith published his rule in 1892 and it has outlived every attempt to replace it, because it is simple enough to do in your head at a map.

**Naismith's rule**

```
Time = distance ÷ 3 mph + ascent ÷ 2,000 ft per hour
```
- In metric: one hour per 5 km of distance, plus one hour per 600 m of ascent.
- Worked: 10 miles with 2,500 ft of ascent is 10 ÷ 3 = 3.33 hours plus 2,500 ÷ 2,000 = 1.25 hours, giving 4 hours 35 minutes.
- It assumes a fit walker on reasonable ground, and it counts no time for breaks, navigation, photographs or lunch.

> **What it does not include** — Descent, rest, terrain, load, weather, navigation, and the party you are walking with. Naismith gives you the moving time of a fit individual on decent ground. Every correction below exists because one of those omissions turned out to matter.

## Aitken's correction: what you are walking on

Aitken proposed in 1977 that the 3 mph base pace only holds on paths, tracks and roads, and that everything else — heather, bog, boulder field, open hillside — should be walked at 2.5 mph. The ascent term stays as Naismith had it.

**10 miles with 2,500 ft of ascent**
| Method | Estimate |
| --- | --- |
| Naismith (1892) | 4 h 35 m |
| Aitken, on paths and tracks | 4 h 35 m |
| Aitken, off path | 5 h 15 m |

Forty minutes on a ten-mile day, purely for the ground underfoot. On an all-day route across open moor that difference is the gap between finishing in daylight and finishing with a head torch.

## Tranter's corrections: who is doing the walking

Tranter's corrections, reproduced in Langmuir's Mountaincraft and Leadership, take the Naismith estimate and adjust it for the fitness of the walker and for fatigue over a long day. Fitness is defined by a test: how many minutes it takes you to climb 1,000 ft over a horizontal half mile. Fewer minutes means fitter.

**The same 10-mile, 2,500 ft route with a Naismith base of 4 h 35 m**
| Fitness (minutes for the test climb) | Corrected time |
| --- | --- |
| 15 — very fit | 2 h 26 m |
| 20 — fit | 3 h 59 m |
| 25 | 4 h 59 m |
| 30 | 6 h 01 m |
| 40 | 6 h 46 m |
| 50 — unfit | 7 h 40 m |

This is the correction that matters most, and it is the one no app applies, because it requires the walker to be honest about themselves. The spread from very fit to unfit on the same route is more than five hours. A route that is a comfortable afternoon for one person is a serious undertaking for another, and the map cannot tell you which you are.

> **Rough ground drops your fitness level** — Tranter also handles terrain, but differently from Aitken: instead of slowing the pace, rough ground effectively drops you one fitness tier and very rough ground drops you two. So a fitness-20 walker on rough ground is treated as fitness 25, and on very rough ground as fitness 30 — turning 3 h 59 m into 4 h 59 m and then 6 h 01 m. It is a blunter instrument than Aitken's and it produces a larger penalty.

Tool: [Estimate a route time](https://dothecalculation.com/calculators/hiking-time-estimator-calculator) — Naismith's rule with the Aitken and Tranter corrections, from distance and ascent.

## Using an estimate sensibly

- Add your breaks separately. Naismith and both corrections give moving time; lunch, photographs and navigation stops are yours to add.
- A party walks at the pace of its slowest member, not its average one. Estimate for the slowest.
- Steep descent is not free. Naismith ignores it entirely, and on rough or steep ground descending can be slower than ascending.
- Work out your own Naismith factor. Time a route you know, compare it with the estimate, and you have a personal multiplier that is worth more than any published correction.
- Have a turnaround time and keep it. An estimate that runs long is only dangerous if you keep going anyway.

## What the pack should weigh

REI publish the guideline most hikers work to, and state it as a percentage of body weight rather than an absolute figure: "A loaded backpacking pack should not weigh more than about 20 percent of your body weight" and "A loaded day hiking pack should not weigh more than about 10 percent of your body weight."

**Target pack weight by body weight**
| Body weight | Day hike (10%) | Backpacking (20%) |
| --- | --- | --- |
| 120 lb | 12 lb | 24 lb |
| 150 lb | 15 lb | 30 lb |
| 160 lb | 16 lb | 32 lb |
| 200 lb | 20 lb | 40 lb |

> **REI's own caveat is worth keeping** — They call these "very general guidelines" and note that they "don't work in every situation. For instance, very petite backpackers will often end up carrying more than 20 percent because you can only get your pack weight so low." A tent, a sleeping bag and a stove weigh what they weigh regardless of who is carrying them.

## Where the weight actually is

Pack weight splits into base weight — everything that does not get consumed — plus food, water and fuel, which shrink as you go. Here is a four-day trip for a 160 lb hiker.

**A four-day trip, 160 lb hiker, 20 lb base weight**
| Component | Weight |
| --- | --- |
| Base weight (pack, shelter, sleep system, clothing, everything else) | 20.0 lb |
| Food, 1.5 lb per day for 4 days | 6.0 lb |
| Water, 2 litres | 4.4 lb |
| Fuel | 1.0 lb |
| **Total at the trailhead** | **31.4 lb** |
| As a share of body weight | 19.6% — just inside the guideline |

Two things fall out of that table. Base weight is the only part you can reduce before you leave, and it is where lightweight backpacking does all its work. And water is heavier than people expect — a litre weighs 2.2 lb, so carrying three litres instead of two costs you the same as an extra day and a half of food.

> **Carry water, or carry the means to get it** — Water is the one item where the right answer changes with the route. On a ridge with no sources you carry all of it. On a valley walk crossing streams every hour, a filter weighing a few ounces replaces several pounds of carried water. Plan the water from the map, not from habit.

Tool: [Total up your pack](https://dothecalculation.com/calculators/camping-pack-weight-calculator) — Base weight, food, water and fuel added up and compared against the 10% and 20% body weight guidelines.

## The two numbers are connected

Neither Naismith nor either correction accounts for load, which is the obvious gap when you put the two halves of this guide side by side. A fit walker carrying 35 lb is not moving at their unloaded pace, and no published correction turns pounds into minutes.

The practical approach is to treat the load as a fitness penalty: if you are carrying a full multi-day pack, estimate yourself a tier less fit than you are on a day walk. It is not rigorous, but it is honest about the direction and the rough size of the effect, which is better than ignoring it.

## Naismith in metric, for common day routes

Most maps outside the United States are in kilometres and metres, and the metric form of Naismith is simpler to use in your head: an hour for every 5 km, plus an hour for every 600 m of ascent. Here it is for a range of typical day walks.

**Naismith moving time, before any corrections or breaks**
| Distance | Ascent | Naismith time |
| --- | --- | --- |
| 5 km | 0 m | 1 h 00 m |
| 10 km | 0 m | 2 h 00 m |
| 10 km | 500 m | 2 h 50 m |
| 15 km | 800 m | 4 h 20 m |
| 20 km | 1,000 m | 5 h 40 m |
| 20 km | 1,500 m | 6 h 30 m |

Notice how much the ascent term contributes. On the 20 km, 1,500 m route, climbing accounts for two and a half of the six and a half hours. On hilly routes, the number on the map that matters most is often the total ascent rather than the distance, and it is the number people most often forget to add up, because it has to be counted from the contour lines rather than read off a single figure.

## Coming down: Langmuir's descent corrections

Naismith treats descent as free, and walkers know it is not. Langmuir's corrections, reproduced alongside Naismith's rule, address it with two adjustments based on how steep the descent is.

- **Gentle descent,** slopes between 5 and 12 degrees: subtract 10 minutes for every 300 m of descent. Walking gently downhill is genuinely faster than walking on the flat.
- **Steep descent,** slopes greater than 12 degrees: add 10 minutes for every 300 m of descent. Steep ground downhill is slow, careful and tiring on the knees.

On the 10-mile route used earlier in this guide, 2,500 feet of descent is about 762 metres. If that descent is gentle, Langmuir takes about 25 minutes off the estimate; if it is steep, he adds about 25 minutes. The same route can therefore vary by nearly an hour depending only on the character of the way down, which the map's contour spacing will tell you before you set out.

## A different approach: Tobler's hiking function

Naismith adds time for climbing. The geographer Waldo Tobler took a different approach in 1993, modelling walking speed directly as a function of slope. His formula is often used in mapping and geographic analysis to estimate travel times across terrain.

**Tobler's hiking function**

```
Walking speed (km/h) = 6 × e^(−3.5 × |gradient + 0.05|)
```
- Gradient is rise over run: a 10% uphill is 0.10, a 10% downhill is −0.10.
- On flat ground it gives about 5 km/h, matching Naismith's base pace. The fastest speed, 6 km/h, comes on a slight downhill of about 5%.
- For off-path travel, the speed is multiplied by 3/5.

**Tobler walking speed by gradient**
| Gradient | On a path | Off path (× 3/5) |
| --- | --- | --- |
| −30% (steep down) | 2.50 km/h | 1.50 km/h |
| −20% | 3.55 km/h | 2.13 km/h |
| −10% | 5.04 km/h | 3.02 km/h |
| −5% | 6.00 km/h | 3.60 km/h |
| 0% (flat) | 5.04 km/h | 3.02 km/h |
| +5% | 4.23 km/h | 2.54 km/h |
| +10% | 3.55 km/h | 2.13 km/h |
| +20% | 2.50 km/h | 1.50 km/h |
| +30% (steep up) | 1.76 km/h | 1.06 km/h |

Tobler captures something Naismith misses: steep descents are slow. A 30% downhill comes out at the same speed as a 20% uphill. It also shows the fastest walking is on a gentle downhill, which matches Langmuir's gentle-descent correction.

**Naismith against Tobler on a steady uphill, on a path**
| Gradient | Naismith equivalent speed | Tobler speed |
| --- | --- | --- |
| 0% | 5.00 km/h | 5.04 km/h |
| 5% | 3.53 km/h | 4.23 km/h |
| 10% | 2.73 km/h | 3.55 km/h |
| 20% | 1.88 km/h | 2.50 km/h |
| 30% | 1.43 km/h | 1.76 km/h |

On sustained climbs Naismith is the more cautious of the two, predicting slower progress than Tobler at every gradient. That is not necessarily a flaw: Naismith's rule comes from hill walking, and a cautious estimate is the safer one to plan a day around. The two agree on the flat, and the gap between them is a reminder that every one of these methods is a model, to be checked against your own timed walks.

## Turning an estimate into a plan

A time estimate is only useful if it becomes a plan with a margin in it. The steps are simple enough to do on the back of the map.

- **Start from the corrected moving time,** using the fitness level of the slowest member of the group.
- **Add breaks explicitly.** A short stop every hour and a longer lunch can easily add an hour to a full day.
- **Add the descent correction** if the way down is steep.
- **Compare the finish time with sunset,** and keep a margin for the unexpected, such as a wrong turn, a slow stretch or weather.
- **Set a turnaround time** before you start: the latest time you will turn back if you have not reached a certain point. Decide it at home, when the decision is easy.

**Illustrative day plan: the 10-mile, 2,500 ft route at Tranter fitness 30**
| Item | Time |
| --- | --- |
| Corrected moving time (fitness 30) | 6 h 01 m |
| Steep descent, Langmuir correction for 762 m | + 25 m |
| Breaks, one short stop an hour plus lunch | + 1 h 00 m |
| Total | about 7 h 26 m |
| Start at 08:30 | Finish about 15:56 |

If sunset that day is 18:00, the plan leaves about two hours in hand, which is a reasonable margin for a route of that length. If sunset is 16:30, it leaves barely half an hour, and a start earlier in the morning or a shorter route is the sensible change. The arithmetic is trivial; the value is in doing it before you leave rather than on the hill.

## Cutting base weight where it counts

The worked pack above had a 20 lb base weight. Base weight is where reductions last for the whole trip, because consumables shrink as you go and gear does not. An informal but widely used label in lightweight backpacking calls a base weight under about 10 lb ultralight; it is a community convention, not a standard, but it shows the scale of what is possible.

- **Start with the three heaviest items.** Shelter, sleep system and pack usually make up most of the base weight. A lighter version of each saves more than trimming dozens of small items.
- **Weigh everything.** A kitchen scale and a spreadsheet turn guesses into numbers, and the numbers are usually surprising.
- **Question duplicates.** Two of anything is often one too many, apart from safety items.
- **Do not cut safety to hit a number.** Navigation, warmth, rain protection, first aid and light are not the place to save grams.
- **Re-check the percentage.** A lighter base weight lets you carry more water or food on the same body-weight guideline, which on a dry route may matter more than the weight saved.

## Common planning mistakes

- **Planning with the fittest walker's pace.** The group moves at the pace of its slowest member.
- **Forgetting ascent.** Distance alone badly underestimates hilly routes.
- **Ignoring descent.** Steep ground downhill is slow; add Langmuir's correction.
- **Leaving breaks out of the estimate.** Every method here gives moving time only.
- **No turnaround time.** Decide in advance when you will turn back.
- **Carrying water you do not need, or not enough.** Plan water from the route's sources, not from habit.

## Comparing two routes: Scarf's equivalence

Naismith's rule has a neat by-product. If three miles of walking takes the same time as 2,000 feet of climbing, any climb can be converted into an equivalent flat distance. Scarf formalised this as equivalent distance = horizontal distance + 7.92 × climb, where 7.92 is the ratio of 15,840 feet (three miles) to 2,000 feet. For convenience an 8-to-1 rule is often used.

**Equivalent flat distance, using Scarf's 7.92 ratio**
| Route | Equivalent flat distance | Time at 5 km/h |
| --- | --- | --- |
| 10 km, 500 m of ascent | 14.0 km | 2 h 48 m |
| 12 km, 900 m of ascent | 19.1 km | 3 h 50 m |
| 14 km, 300 m of ascent | 16.4 km | 3 h 17 m |
| 20 km, 1,500 m of ascent | 31.9 km | 6 h 23 m |

The comparison between the middle two rows is the point. The 12 km route is shorter on the map than the 14 km one, but its extra 600 m of climbing makes it the longer day by about half an hour. Equivalent distance puts both on one scale so you can compare them at a glance. The small difference from the metric Naismith times earlier in this section comes from rounding: the metric form of Naismith uses 5 km per hour and 600 m per hour, a ratio of about 8.33, while Scarf's figure of 7.92 comes from the original imperial units.

## Building your own correction factor

Every correction in this guide is a general model. The most accurate one available is your own, and it takes only a couple of walks to build. Time a route you know, subtract your breaks, and divide your actual moving time by the Naismith estimate for that route.

**Illustrative: a personal factor from one timed walk, applied to a new route**
| Step | Working | Result |
| --- | --- | --- |
| Known route: 10 km with 500 m of ascent | Naismith estimate | 2 h 50 m (170 min) |
| Your actual moving time, breaks removed | Timed on the day | 3 h 20 m (200 min) |
| Personal factor | 200 ÷ 170 | 1.18 |
| New route: 20 km with 1,500 m of ascent | Naismith 6 h 30 m × 1.18 | about 7 h 39 m |

One walk gives a rough factor; three or four on different kinds of ground give a reliable one, and you will often find it differs between paths and rough ground, or between short days and long ones. Keep separate factors if it does. Recalculate after a long break from walking or a change in fitness, and apply the factor for the slowest member whenever you walk as a group.

## Sources

- Naismith's rule as originally published in 1892: one hour per 3 miles (5 km) plus one hour per 2,000 ft (600 m) of ascent.
- Aitken (1977) for the split base pace: 3 mph on paths, tracks and roads, 2.5 mph on everything else, with the ascent term unchanged.
- Tranter's corrections for fitness and fatigue, as reproduced in Langmuir, Mountaincraft and Leadership. Fitness is defined by the minutes taken to climb 1,000 ft over a horizontal half mile.
- REI Expert Advice, "How Much Should Your Pack Weigh?" — the 20% backpacking and 10% day hiking guidelines and the caveat that they are very general and do not fit every hiker: https://www.rei.com/learn/expert-advice/backpacking-weight.html
- Water weight uses the standard 1 litre = 1 kg = 2.20462 lb conversion.

## Where to go next

For the navigation half of the same day out, [geocaching coordinate maths](/blog/hobby/geocaching-coordinate-math) covers projecting a waypoint from a bearing and a distance, working out distance and bearing between two points, and the magnetic declination correction that stops a compass bearing sending you into the wrong valley.

## Common questions

**What is Naismith's rule?**

Allow one hour for every 3 miles of distance plus one hour for every 2,000 feet of ascent. A 10-mile route with 2,500 feet of climbing comes to 4 hours 35 minutes. It is moving time for a fit walker on reasonable ground, with no allowance for breaks or for descent.

**Is Naismith's rule accurate?**

For a fit walker on good paths, surprisingly so for something published in 1892. It breaks down off-path, for walkers who are not fit, and on long days where fatigue builds. Aitken's correction handles the first and Tranter's handles the other two — and Tranter's makes by far the biggest difference, up to five hours on the same route.

**How much should my backpack weigh?**

REI's guideline is no more than about 20% of your body weight loaded for backpacking, and about 10% for a day hike — so 30 lb and 15 lb for a 150 lb hiker. They note these are very general, and that petite hikers often exceed 20% simply because gear has a floor weight.

**How much does water weigh?**

One litre weighs 1 kg, or 2.2 lb. Three litres is 6.6 lb, which is more than four days of food at 1.5 lb a day. If the route has reliable water, a filter weighing a few ounces replaces several pounds of carried water.

**What is base weight?**

Everything in your pack that you do not consume — the pack itself, shelter, sleep system, clothing and gear — excluding food, water and fuel. It is the number lightweight backpackers quote because it is the part you can actually reduce before you leave the house.

**Does carrying a heavy pack slow you down?**

Yes, substantially, and none of these time formulas account for it. There is no published correction turning pounds into minutes, so the practical workaround is to estimate yourself one Tranter fitness tier lower when carrying a full multi-day load.

**How long does it take to walk 10 km with 500 m of ascent?**

Naismith's rule gives about 2 hours 50 minutes of moving time: 2 hours for the distance at 5 km/h plus about 50 minutes for 500 m of ascent at 600 m per hour. Add breaks, a descent correction if the way down is steep, and adjust for the fitness of the slowest walker.

**Does walking downhill take time?**

It depends on the gradient. Langmuir's corrections subtract 10 minutes per 300 m of descent on gentle slopes of 5 to 12 degrees, and add 10 minutes per 300 m on slopes steeper than 12 degrees. Tobler's hiking function agrees that steep descents are slow: a 30% downhill is about as slow as a 20% uphill.

**What is Tobler's hiking function?**

A formula from Waldo Tobler (1993) that gives walking speed from slope: 6 × e^(−3.5 × |gradient + 0.05|) km/h. It gives about 5 km/h on the flat, a maximum of 6 km/h on a slight downhill, and should be multiplied by 3/5 for off-path travel.

**Is Naismith or Tobler more accurate?**

They agree on the flat. On sustained climbs Naismith predicts slower progress than Tobler, which makes it the more cautious planning figure. Neither knows your fitness or the terrain, so time a few of your own walks and compare them with both.

**What is a turnaround time?**

The latest time you will turn back if you have not reached a set point on the route. Decide it before you set out, from your estimate, your breaks and the time of sunset, so that the decision on the hill is already made.

**How do I compare a short steep route with a longer flat one?**

Convert each to an equivalent flat distance with Scarf's equivalence: horizontal distance plus 7.92 times the climb, in the same units. A 12 km route with 900 m of ascent comes to about 19.1 km, longer in time than a 14 km route with 300 m, which comes to about 16.4 km.

---

_Source: [Do The Calculation](https://dothecalculation.com/blog/hobby/hiking-time-and-pack-weight). Quote freely with attribution and a link to this page._