How to Calculate the Number of Screws Required for a Deck

Hunker may earn compensation through affiliate links in this story.

You want to build a deck in your backyard, but for first time builders, it may seem difficult – especially if you don't know how many screws are needed to build the deck. Choosing the right deck fastener is already a nuisance, but figuring out the number of deck screws isn't. All you need to know is the basis for understanding estimation methods as well as how to calculate the number of fasteners you need per board.

How to Calculate the Number of Screws Required for a Deck
Image Credit: Trish233/iStock/GettyImages

Basics of Screwing Down Deck Boards

When you start a deck building project, it's important that you purchase corrosion-resistant screws. They are the preferred screw because you can fasten pressure-treated decks and they will not corrode or loosen over the years. When you start the installation, you have to secure each board down with a couple of screws. Most of the fastening is done once the boards are tacked down. It's essential that you calculate the screw length correctly or the boards will split.

How to Calculate the Amount of Fasteners Needed Per Board

For standard deck fasteners, the rule of thumb is that you need 350 screws for every 100 square feet of decking. If you're good at math, calculating this equation will be a breeze. If you find multiplication and finding measurements confusing, though, there are deck calculators that will do all of the work for you. All you have to do is answer a couple of fundamental questions regarding your deck, and it will estimate the number of fasteners that you will need. At the end of the day, unless you like figuring out equations, the online calculators are life savors.

Step 1: Measure Your Deck

Before you even access how many screws you need, it's important to measure how large your deck is. To calculate the number of screws you need, you have to know the length and width of the entire deck. This will help you determine the square footage of the deck.

Step 2: Measure the Joist Spacing

A joist is the skeleton bones of the deck. The joist is what holds the planks on your deck in place. Afterward, you're going to measure the length and width of each of the deck boards. You need to calculate how many deck boards are needed for the deck.

Step 3: Count How Many Screws You Need

You have to figure out how many screws you want at each joist intersection. You should have at least two screws per intersection. Depending on how you want the design width of the deck to look, though, is how many screws you will add. Afterward, you will calculate how many screws are needed. The math will be two screws per joist times the number of joists times the number of decks on the board.


Allanah Dykes is a freelance writer and her work has been featured on Elite Daily, Levo League, Popsugar, Complex, Gurl, The Kitchn, HelloGiggles, Revelist, and Food 52.

View Work