How to calculate deck footings

Updated March 22, 2017

Deck footings are vital to the construction of a deck as they establish a solid foundation for building the deck. Deck footings typically are driven underground and encased in cement to provide extra stability. It is therefore imperative to make proper deck footings calculations based on the area and measurements of the deck to ensure your deck will be properly supported and safe. Serious injury could occur if a deck collapses due to poorly sized deck footings. Representatives at a local hardware or home improvement store could offer additional advice about building a deck.

Measure the length and width of the deck that you are going to install, and multiply the two numbers to obtain the area of the deck.

Divide this area by two, as most standard rectangular decks are built with two footings with the weight evenly distributed between them. If you are going to use more than two footings, divide the area by the total number of footings you are going to use.

Multiply this number by 55, which is the pounds per square foot. This will give you the total load, or area supported, by one footing.

Consult the deck footing sizing chart and match the total load with the surface the footing will be buried in (gravel, soil, etc.) This chart is available both online and at a local hardware or home improvement store. The chart will tell you how long to make your footings.


Contact your local building department to double check your calculations before starting to build your deck.

Things You'll Need

  • Calculator
  • Measuring tape
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About the Author

James Wiley graduated from Providence College in 2009 as a double major in global studies and Spanish. Wiley's capstone thesis paper was published in the Providence College database. He has also competed in international script-writing competitions and coauthored a pilot which placed in the top 15 percent of international entries over the past year.