Boards Needed: Total deck boards to span the deck width, based on board width plus your chosen gap. Buy 10–15% extra for waste from cuts.
Deck Area: The footprint of the deck in square feet — useful for comparing to your local building code's permit threshold.
Board Feet: A lumber measurement (1 board foot = 1 ft × 1 ft × 1 in). Lumber yards often price decking by the board foot.
Screws: Approximate deck screw count assuming 16-inch joist spacing with two screws per board at each joist crossing.
How This Calculator Works
You enter the deck's length and width in feet, your board's nominal width in inches, and the spacing gap between boards. The tool divides the deck width by the combined board-plus-gap width to find how many boards span the surface. It then calculates board feet and estimates screws at two per board per joist, assuming 16-inch joist spacing.
Quick Questions
What gap should I use between boards?
Use 1/8 inch (0.125") for composite decking and 1/8" to 3/16" for pressure-treated wood, which will shrink as it dries.
Does this account for waste from cuts?
No. Add 10–15% to the board count for end cuts, staggered joints, and any angled edges.
What does 5.5-inch board width mean?
A standard 2×6 deck board has an actual width of 5.5 inches. A 2×4 is actually 3.5 inches wide.
Do I need different screws for composite?
Yes. Composite decking requires specially designed screws with smaller heads and reverse threads to avoid mushrooming the material.