Naismith Rule Hiking Time Calculator

The Naismith Rule was devised by Scottish mountaineer William W. Naismith in 1892 and remains the most widely used formula for estimating hiking time.

The rule: Allow 1 hour for every 5 km of horizontal distance, plus 1 additional hour for every 600 m of ascent.

Descent is generally not added in the classic rule (Naismith assumed descending took about the same time as flat terrain), though some versions add 10 minutes per 300 m of steep descent.

Fitness adjustments (Tranter’s corrections):

• Very fit: reduce by 20%
• Average: no change
• Unfit: add 50%
• Carrying a heavy pack: add 20-30%

Example: A trail is 12 km with 900 m of ascent.

• Flat time: 12/5 = 2.4 hours
• Ascent time: 900/600 = 1.5 hours
• Total: 3.9 hours ≈ 3 hours 54 minutes

Limitations: The Naismith Rule assumes good trail conditions and a moderately fit hiker moving steadily without long breaks. Add time for rest stops, photography, navigation, and bad weather. In rough off-trail terrain, a correction factor of 1.5–2× is often needed.

Practical tips: Most day hikers average 3–4 km/h on flat trails with 200–300 m/h of climbing rate. Alpine mountaineers typically use 300–400 m/h of ascent in the Naismith formula.

How it compares to Tobler. The other common model, the Tobler hiking function, predicts speed from gradient rather than adding a flat penalty per meter climbed. On the 12 km / 900 m example above, Naismith says 3.9 hours and Tobler worked leg by leg says about 3.4. Naismith is the more conservative of the two, and for a full day in the hills that is usually the safer error to make. Tobler earns its keep when the ground is unusual: a long gentle descent, where Naismith charges you nothing at all and Tobler correctly speeds you up, or a route with one sustained steep grade rather than a mix.

One thing neither model does is charge for going down. Naismith assumed descent takes about as long as flat ground. On a good path that holds up. On loose scree, wet roots or anything exposed, descent is frequently the slowest part of the day, and both models will tell you a time you cannot walk.