Naismith's Rule (estimate walking time) 
Naismith's rule was developed by a William Naismith in 1892 as a basic rule of thumb that can be used to calculate the time it will take to walk from point a to b. The formula has been adapted a little since then and considers the distance to walk, the altitude changed and the speed that you will walk at.
This rule assumes a reasonable level of fitness, but Tranter's corrections can but used to change the time to suit a particular level of fitness.
Naismith's Rule first makes a calculation based on distance over time. eg if your walking a 4km/h for 4 km it will take you one hour. Not rocket science. But it adds a bit over an hour and a half for every 1000m you climb and about three quarters of a hour for every 500 meters you descend.
I have include two methods to help you in your trip planning. Firstly a calculator and secondly a Nomogram that you can use with a ruler in the field. Have a play with both
How to use Naismith's Rule NomogramAt first this Nomogram can be a bit overwhelming to look at. But don't stress I think you will pick it up quickly.
First you need to pick an altitude shift line. Move from right to left to find the line that represents the number of meters you will climb in total, next Move down the number of meters you will descend in total.
Follow this new line up and to the left (this is your altitude shift line)
see here we plan to climb 700m and descend 1000m
Next we keep going up the altitude shift line until we get to your estimated walking speed. This is our pivot point.
In this example it is 4km/h
Now just draw a straight line from the number of Kilometers you plan to walk, through the pivot point till you hit the Hours axis. And voila you can read the estimated time.
In this example we will walk 10km and the answer is 4 and a half hours
If you wish to apply Tranter's Corrections I have include a table below to help. Fitness in the left column is the number of minutes that it would take you to climb 1000ft over 800m
