Deck Calculator
Boards, framing, stairs, and railing — everything for a rectangular deck.
5.5" is standard 5/4×6
1/4" typical
Boards, framing, stairs, and railing — everything for a rectangular deck.
5.5" is standard 5/4×6
1/4" typical
Decking boards, joists, screws, stairs, and railing for a rectangular deck — the full material list, not just the boards.
The number of board rows is the deck's width divided by the board width plus the gap between boards, rounded up, with 10 percent added for waste. Joists are the deck's length divided by the on-center spacing (16 inches is typical), plus one, because a run of joists needs one more than the number of spaces. Screws come out at roughly 350 per 100 square feet of decking.
Example
A 12 × 16 foot deck with 5 1/2-inch boards and a 1/4-inch gap needs about 34 rows of board, and about 670 deck screws — call it one 5-pound box.
About 34 rows of 5 1/2-inch board across a 12-foot width, once you allow a 1/4-inch gap between boards and 10 percent for waste. Multiply by the length you are buying to get your board count.
16 inches on center is standard and safe for most decking. Go to 12 inches if you are laying boards diagonally, or if you are using a composite that specifically calls for it.
About 1/4 inch for dry boards. If your lumber is wet pressure-treated stock straight off the pile, you can lay it much tighter — it will shrink and open its own gap as it dries.