How to Estimate Hiking Time With Naismith's Rule

Twelve kilometres with 750 metres of ascent. Naismith’s rule says three hours forty. You’ll probably be out for four and a half, and if the ground is rough or the group is mixed, longer.

The rule is a good starting point and a poor finishing point, and knowing what it omits is what turns it into a usable plan.

The rule

Naismith’s rule, devised by a Scottish mountaineer in 1892, allows:

• 5 km/h on the flat
• Plus one hour for every 600 m of ascent

time = distance ÷ 5 + ascent ÷ 600

For 12 km and 750 m: 2.4 + 1.25 = 3.65 hours, or 3 hours 39 minutes.

Note that’s total ascent, not the height difference between start and finish. A route that goes up and down repeatedly accumulates far more ascent than its summit height suggests, and reading total ascent off a mapping app rather than estimating it is the single biggest improvement you can make to the input.

What it leaves out

Descent. Naismith ignores it entirely, which is fine for gentle downhill — slightly faster than flat — and wrong for steep. Steep or loose descent is slower than the flat and considerably harder on the knees. Some corrections subtract time for gentle descent and add for steep.

Fitness and load. Naismith assumed a fit walker on good ground. Tranter’s corrections adjust for individual fitness and for fatigue over a long day, and they make a substantial difference — a less fit walker on hour seven may be at half the assumed pace.

Ground conditions. Path versus bog, rock versus grass, snow versus dry. Rough ground can halve your speed and it doesn’t appear in the formula at all.

Breaks. This is the big one. Moving time is not elapsed time. Lunch, layers, navigation checks, photographs and regrouping routinely add twenty to thirty percent on a full day.

Group size. A group moves at the pace of its slowest member, and stops more often. Add time for anything above three or four people.

Using it safely

Compare the total against daylight. Work out your latest acceptable turnaround time before setting off, and know where the escape routes are. A plan that only works if everything goes right isn’t a plan.

The mountain safety guidance published by national bodies covers this properly, and it’s worth reading before a first hill day rather than during one.

Common mistakes to avoid

• Using the height of the summit instead of total ascent.
• Planning to moving time and being surprised by elapsed time.
• Assuming the return leg takes the same as the outward — it’s usually slower.
• Ignoring that everyone slows in the last third of a long day.
• Building a plan with no turnaround time and no escape route.

How to do it with Hiking Time Calculator

The Hiking Time Calculator applies Naismith and adds the break allowance it omits.

1. Enter the route distance and total ascent, from a mapping tool rather than an estimate.
2. Choose a pace band honestly — Naismith’s baseline assumes a fit walker on good ground.
3. Read moving time and estimated elapsed time separately.
4. Compare against daylight and set a turnaround time before you leave.

Other outdoor planning tools are in the tools directory.

Frequently asked questions

Is Naismith’s rule accurate?

It’s a reasonable base for a fit walker on a good path, and optimistic for most people. Corrections such as Tranter’s adjust for fitness and fatigue, and rough ground can add a great deal.

Does descent take no time?

Naismith ignores it, which is wrong on steep ground. Gentle descent is slightly faster than the flat; steep or loose descent is slower and much harder on the knees.

Why add so much for breaks?

Because moving time isn’t elapsed time. Lunch, navigation, photographs and layer changes routinely add twenty to thirty percent on a full day.

Final thought

Take Naismith’s answer, add a third, and compare it against the daylight you have. If the margin makes you uncomfortable, shorten the route rather than the estimate.

Try the free Hiking Time Calculator