How to Calculate Deck Boards
Building a deck is one of the most rewarding DIY projects, but running out of decking boards mid-project is a nightmare. Our deck board calculator takes the guesswork out of your material list by converting your total square footage into exact linear feet, and then dividing by your chosen board length to tell you exactly how many boards to buy.
The Math Behind the Calculator
First, we calculate the total square footage of your deck (Length × Width). Next, we convert your board width from inches to feet. By dividing the total square footage by the board width in feet, we get the total linear feet of decking required. Finally, we apply a waste factor and divide by the length of the boards you are purchasing to get your final board count.
Frequently Asked Questions
What is the standard width of a deck board?
The most common decking board is a "5/4 x 6" board, which actually measures 5.5 inches wide. Standard 2x4s measure 3.5 inches wide, and 2x8s measure 7.25 inches wide.
How much gap should I leave between deck boards?
You should leave a 1/8 to 1/4 inch gap between boards for water drainage. Our calculator assumes standard spacing. If you are using hidden fastener clips, the clip itself automatically sets the correct gap.
How deep do deck footings need to be?
Deck footings must extend below your local frost line, which varies by region. This calculator covers the decking boards themselves — for the concrete volume needed for footings, posts, or sonotube piers, use our Concrete Footing & Sonotube Calculator.
What is standard deck railing spindle spacing?
Most building codes require baluster (spindle) gaps no wider than 4 inches, so a sphere that size can't pass through. For a typical 8-foot railing section with 2-inch wide balusters, that usually works out to 16-18 spindles, but always verify exact spacing against your local code before installing.