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How to Calculate the Ladder Length Needed

Ladders are needed to work at heights taller than ourselves. When working on ladders you need to do so safely in order to avoid a possible trip to the emergency room. Choosing the right length of the ladder helps to work on the ladder safely.

Stepladders must be tall enough for the worker to reach the area of work with their hands. A stepladder is suited for work up to a height of about 10 feet. Beyond that height, extension ladders are better suited.

Stepladders
Determine the height of the stepladder needed based on the height of the work area. A step ladder should reach within four feet of the work area so the worker can stand on the rung and safely reach the work area.

infographic of extension ladder pitch and placement

Here’s the calculation to determine the height of a step ladder: If your ceiling is 12 feet in height, subtract the four feet needed for the worker to reach the work area, and the remainder would be the height of the step ladder needed, in this case, a 8 foot step ladder.

Extension Ladders
Extension ladders need to be long enough to be placed at the correct pitch depending on the work height needed. If you are working on a roof, you need the extension ladder to extend three feet above the eave so you can access the rooftop with ease. So make sure to consider and add in this additional length when determining the height needed.

Here’s the calculation to determine the pitch of the extension ladder: place the feet of the ladder one (1) foot away from the wall for every four (4) feet of extended ladder height. An example would be a twenty (20) foot extended ladder (divided by four) should be placed five (5) feet away from the wall.

Talk with Our Ladder Experts
If you are still not sure what length of ladder you need, give us a call! We at Sunset Ladder & Scaffold have been selling ladders and scaffolding since 1929. Our team of experts are the best informed in the ladder and scaffold industry with sales and service second to none! We are ready to advise you of the many options available to you.


About Sunset Ladder & Scaffold
Sunset Ladder and Scaffold rents and sells the safest and highest quality ladders, scaffolding and related products available since 1929. We rent and sell ALL types of ladders and scaffolding that the industry offers including our own American-made Sunset Ladder Co and EZ Lift™ brands.

2 thoughts on “How to Calculate the Ladder Length Needed

  1. Your website is great. One question: I have a 14 high wall on my house. I realize that the ratio for determining ladder height and set back from the wall is 1:4. If I have an 18 foot ladder, the set back would be 3.5 feet. What I don’t know is how much I would lose on the top since I need about 3 feet above the height of the wall to be safe.

    1. Hi Steve,
      To answer your question, the 1:4 ratio is just a guideline. So your 18 foot ladder divided by 4 equals 4.5 foot set back approximately (not the 3.5 you thought) … Your 18 foot ladder would reach an approximately height of 10 feet safely.

      We have a extension ladder chart on a previous article The Right Size Ladder for a Two Story Home that will help with the calculations. I got this chart from OSHA.

      To answer your question “read the chart backwards”. You know you need to reach a vertical height of 14 feet. Plus you need 3 feet beyond that to work safely, so a total of 17 feet in vertical height. Look in the fourth column, find the highest point your ladder will reach, and there’s a choice of 13 to 17 feet… according to the chart, you would need to set the extension ladder back 6 feet from the wall at the base. Then you would need a 24 foot extension ladder for the job. I hope this helps!

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