Enter the height of the object the ladder is leaning on to determine the correct ladder height.

Ladder Height Formula

The following formula is used to calculate a ladder height. 

LH = SQRT (H^2 + (H/4)^2) + 2
  • Where LH is the ladder height (ft)
  • H is the height of the object that needs to be reached (ft)

What is the correct ladder height?

A ladder should always be placed at an angle of roughly 75 degrees to the surface you are working on. This leads to a “base” length of 1/4 that of the height of the object you are reaching.

Add in 2 extra feet on all surfaces for safety.

How to calculate ladder height?

Example Problem:

The following example problem outlines how to calculate a correct ladder height.

First, determine the height of the object the ladder will be resting on. For this example, a person is working on a roof that is 12 feet tall.

Next, use the formula above to estimate the correct ladder height.

LH = SQRT (H^2 + (H/4)^2) + 2

LH = SQRT (12^2 + (12/4)^2) + 2

LH = 14.369 feet