Hiking Time Calculator: Naismith's Rule for Planning a Day Hike

Naismith's rule, plus three additions

In 1892 the Scottish mountaineer William Naismith proposed a simple way to time a walk in the hills: allow one hour for every 3 miles (5 km) on the map, plus an extra hour for every 2,000 feet (600 m) of ascent. More than 130 years later, Naismith's rule is still the starting point for most hiking time estimates.

moving time (hours) = miles ÷ pace (mph) + feet climbed ÷ 2,000

Naismith assumed 3 miles per hour on the flat. The calculator lets you choose 2, 2.5 or 3.5 instead, because a family with young kids or a group of first-timers rarely holds 3. The climbing allowance stays at Naismith's figure.

On top of that we add three things of our own:

• Rests. Ten minutes for every full hour of moving time. This is our rule of thumb, not part of Naismith. Untick the box if you prefer to count breaks yourself.
• Water. A planning rate of 0.5 liters per hour in mild weather, 0.75 when warm and 1 liter when hot, times 0.85 for an easy effort or 1.25 for a strenuous one, times the number of people. The hot figure lines up with National Park Service desert advice, such as Saguaro National Park's quart of water per hour of hiking on hot days.
• Daylight. The meter compares your total time with the hours of light left and warns you when the hike would use more than 80 percent of them.

Worked example: 6 miles with 1,500 feet of climbing

The calculator opens with a solid half-day outing: 6 miles round trip, 1,500 feet of total climb, Naismith's 3 mph, rests on, 6 hours of daylight left, mild weather, moderate effort, one hiker.

• Walking: 6 ÷ 3 = 2 h 00 min.
• Climbing: 1,500 ÷ 2,000 = 0.75 hours, or 45 min.
• Moving time is 2 h 45 min, which holds two full hours, so rests add 20 min.
• Total: 3 h 05 min.

Water comes to 3.08 hours × 0.5 liters, or about 1.5 liters (51 oz), which the calculator rounds up to 2 one-liter bottles. The hike uses about half of the 6 hours of light, so no warning appears.

Change the weather setting to hot and the water jumps to about 3.1 liters for the same walk. Drop the pace to an easy 2 mph and the total becomes 4 h 15 min, roughly 71 percent of the daylight: still under the warning line, but with little room for a wrong turn.

Where the estimate runs long or short

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Naismith wrote for "men in fair condition" on easy expeditions, and his rule says nothing about descent. Steep downhill sections slow many people, especially on loose rock or with sore knees, and a pair of trekking poles takes some of that load. Snow, mud, scrambling, altitude and heat all add time the formula cannot see. Treat the number as a floor, not a promise. On a humid summer day, run the forecast through the heat index calculator before you pick a weather setting.

In a group, the slowest hiker sets the pace. Enter that person's speed, not the fastest one's.

Turning the estimate into a plan

Set a turnaround time before you start. Half of 3 h 05 min is about 1 h 32 min, so if you leave the trailhead at 1:00 p.m., you should be at the far end by about 2:30. If you are not, turn back anyway. The National Park Service's hiking safety tips also suggest leaving your plan with someone who is not coming along.

If you reach the trail by bus, the last bus home is your real sunset. Enter the hours until that bus as "daylight left," and the meter will tell you whether the plan fits. Our story on transit to trails programs covers the routes and shuttles that make car-free hikes possible.

Carrying all the water you need for a long, hot day gets heavy fast. On routes with reliable streams, a squeeze filter lets you refill along the way, though seasonal creeks can be dry by late summer, so check with the ranger station first. A headlamp belongs in every pack whatever the meter says.

We based these picks on manufacturer specifications, published reviews and feedback from owners, not on our own field trials.

You do not need to buy any of it to start. Public libraries, parks departments and outdoor clubs in many cities run gear libraries that lend day packs and other basics, usually free or for a small fee.

Questions

What is the Naismith rule for hiking time?

The Naismith rule is a hiking time estimate devised by Scottish mountaineer William Naismith in 1892. It allows one hour for every 3 miles (5 km) of distance plus one hour for every 2,000 feet (600 m) of ascent. It does not include rest stops, so many hikers add breaks on top.

How long does it take to hike 5 miles?

At the Naismith pace of 3 miles per hour, 5 miles of walking takes about 1 hour 40 minutes before any climbing. Add 30 minutes for every 1,000 feet of ascent, so a 5-mile hike with 1,000 feet of climb takes about 2 hours 10 minutes of moving time, or about 2 hours 30 minutes with short rests. Slower groups, rough trails and heat can add much more.

How much water should I bring on a day hike?

A common planning range is about half a liter per hour in mild weather and up to 1 liter (about a quart) per hour in the heat, more for hard efforts. For a 3-hour hike in mild weather that means about 1.5 liters per person, and around twice as much on a hot day. Carry extra if there is no reliable water on the route.

How do I estimate hiking time for a slower group?

Use the pace of the slowest member, which for families with children or new hikers is often 2 to 2.5 miles per hour on the flat. Keep the climbing allowance of one hour per 2,000 feet, add rests, and set a turnaround time so the group is back well before dark.

Does the Naismith rule include rest breaks?

No. The Naismith rule estimates moving time only. Our calculator adds an optional 10 minutes of rest for every full hour of moving time, which is our own rule of thumb rather than part of the original rule.