# Naismith's Rule Calculator

> Free online hiking time estimator at naismithsrule.com. Calculate how long a hike will take based on distance, elevation gain/loss, and track difficulty.

## What is Naismith's Rule

Naismith's Rule was developed by Scottish mountaineer William W. Naismith in 1892. It estimates hiking time by allowing 1 hour for every 5 km of horizontal distance, plus 1 hour for every 600 m of vertical ascent.

## How this calculator improves on the original

This calculator adds two refinements to the original formula:

- Descent: Based on Eric Langmuir's 1984 correction, subtracting 10 minutes for every 300 m of descent on a gentle slope.
- Track grade: A five-level terrain difficulty scale that adjusts base walking speed.

### Track grades

| Grade | Description | Speed |
|-------|-------------|-------|
| 1 | Light easy going - vehicle track | 5 km/h |
| 2 | Easy going - well formed bush track | 3 km/h |
| 3 | Medium going | 2 km/h |
| 4 | Bush track, sometimes obscure | 1.5 km/h |
| 5 | Thick bush - heavy going | 0.5 km/h |

## The formula

Time (minutes) = (distance_km / speed) * 60 + (climb_m / 600) * 60 - (descent_m / 300) * 10

The speed values were calibrated through hundreds of kilometres of real hikes in the Australian bush across all weather conditions and track grades.

## Important notes

- Naismith's Rule is a guideline, not a definitive predictor. Actual hiking time varies with weather, fitness, pack weight, and conditions.
- The descent adjustment assumes gentle slopes. Very steep descents may take longer than flat terrain.
- The calculator is free, requires no registration, and runs entirely in the browser with no data collection.

## Pages

- [Calculator](https://naismithsrule.com/): The main hiking time calculator
- [About](https://naismithsrule.com/about.html): History of Naismith's Rule and how the calculator works
- [Privacy Policy](https://naismithsrule.com/privacy-policy.html): Privacy policy

## Author

James Robinson, Scout Leader at 1st Blackheath Scout Group, Blue Mountains NSW, Australia.

## Also available as

- [iOS App](https://apps.apple.com/us/app/naismiths-rule-calculator/id6475137430)