Deck Board Calculator
Calculate the number of deck boards and total linear footage needed for a deck based on its size, board width, and gap spacing.
ft
ft
in
in
Common gap is about 1/4 inch for drainage and expansion
Results
Deck Boards Needed
26
Deck Area
192 sq ft
Total Linear Footage
416 ft
How the Deck Board Calculator Works
Enter your deck's length and width, the width of the decking boards you plan to use, and the gap you'll leave between boards (commonly about 1/4 inch for drainage and seasonal expansion). Each board plus its gap takes up a fixed "effective width" across the deck, so dividing the deck's width by that effective width gives the number of boards needed to span it, running the full length of the deck.
Example
A 16 ft × 12 ft deck using 5.5-inch-wide boards with a 0.25-inch gap has an effective board width of 5.75 inches (about 0.479 ft). Dividing the 12 ft deck width by 0.479 gives about 25 boards, each 16 ft long — for a total of 25 × 16 = 400 linear feet of decking.
Common Use Cases
- Estimating how many deck boards to order before starting a build.
- Budgeting total linear footage of decking material and its cost.
- Comparing material needs between different board widths.
- Planning board layout direction and spacing before installation.
FAQs
Should I add extra boards for waste and cuts?
Yes — this calculator gives the baseline number of boards to fully cover the deck's width. Most builders add 10-15% extra to account for cutting waste, mistakes, and staggered end joints, especially if boards don't come in exactly your deck's length.
Why leave a gap between boards at all?
Gaps allow water to drain through the deck surface instead of pooling, and give the boards room to expand and contract with temperature and humidity changes without buckling or splitting.
What if my boards don't span the full deck length in one piece?
If your deck is longer than the boards you're using, you'll need to join boards end-to-end over a joist, which uses more total linear footage than this calculator's simple length × board-count figure. Account for extra material and staggered seams in that case.