Turn your deck's size into a shopping list of boards, joists, rim board, screws and posts.
This calculator counts materials. It doesn't size joists or beams, check spans or design footings. Those depend on your local building code, lumber species and grade, and the span tables your inspector uses. Check them with your building department before you buy framing.
Deck area: 192 sq ft Decking rows: 26 Pieces per row: 1 Decking linear feet: 416 Boards to buy: 29 Joists: 13, each about 12 ft Rim or band board: 56 ft Screws: 676 (2 boxes of 350) Posts: 3
Each joist is about the deck width long, minus the rim board's thickness. This count is not a span check. Verify joist size, spacing, and footings with your local code.
Enter your deck's size, board width and length, and joist spacing. You'll get the rows of decking, boards to buy with waste, joists, rim board, screws and roughly how many posts to plan for, in a list you can copy or print.
The single biggest swing in board count comes from board length. Each row needs ceil(deck length ÷ board length) pieces, so a 16 ft deck covered with 12 ft boards needs two pieces per row and wastes 8 ft on every row. On a 16 × 12 deck that's 58 boards with 12 ft lumber versus 29 with 16 ft lumber, for the same deck. When you can, choose a board length that matches or evenly divides the deck length. On long decks, plan where the butt joints will land. They need to fall over a joist.
Rows come from the deck's width divided by one board plus its gap. Boards are rows times the pieces each row needs, plus waste, and joists are the deck length divided by your spacing, plus one to close the frame.
With 5.5 in boards, 1/8 in gaps, 16 ft boards, joists 16 in on center and 10% waste: 144 in ÷ 5.625 in = 25.6, so 26 rows. That's 416 linear feet of decking and 29 boards with waste. You'll need 13 joists, 56 ft of rim board, 676 screws (2 boxes of 350) and 3 posts on one beam at 8 ft spacing. These counts match the same example published by other deck calculators.
With 12 ft boards and joists 12 in on center: 22 rows of two pieces each, so 49 boards with 10% waste. Tighter joist spacing means 21 joists (each about 10 ft) and 924 screws, which is 3 boxes. Plan on 4 posts.
With narrow 3.5 in boards, 3/16 in gaps, 10 ft boards, 16 in spacing and 5% waste: 33 rows, 35 boards, 9 joists and 594 screws. Narrow boards look great but take more rows and more screws.
Defaults: 5.5 in boards, 1/8 in gap, joists 16 in on center, 10% waste, 2 screws per crossing, one beam with posts up to 8 ft apart.
| Deck (L × W) | Board length | Rows | Boards | Joists | Screws | Posts |
|---|---|---|---|---|---|---|
| 10 × 10 ft | 10 ft | 22 | 25 | 9 | 396 | 3 |
| 12 × 12 ft | 12 ft | 26 | 29 | 10 | 520 | 3 |
| 16 × 12 ft | 16 ft | 26 | 29 | 13 | 676 | 3 |
| 16 × 16 ft | 16 ft | 35 | 39 | 13 | 910 | 3 |
| 20 × 12 ft | 10 ft | 26 | 58 | 16 | 832 | 4 |
Stairs, railings, joist hangers, flashing, ledger bolts, beam lumber and concrete aren't included. Use the Concrete Calculator for footings. Hidden-fastener clips replace face screws, so if you use them, count one clip per board/joist crossing and check the clip maker's guidance.
Divide the deck width (in inches) by the board width plus the gap to get rows, multiply by pieces per row, and add waste. A 16 × 12 ft deck with 16 ft 2×6 boards needs 26 rows, or 29 boards with 10% waste.
Length × width. A 16 × 12 deck is 192 ft². Board counts depend on rows and board length, not just area, which is why this tool works from dimensions.
About two screws everywhere a board crosses a joist. A 16 × 12 deck with joists 16 in on center works out to 676 screws, or 2 boxes of 350.
Deck length in inches ÷ joist spacing, rounded up, plus one. A 16 ft deck at 16 in on center needs 13 joists. Joist size and span come from your local code, which this tool doesn't check.
The default is 1/8 in, but follow your decking maker's instructions. Wood that's still wet from treatment is often laid tight because it shrinks as it dries.
Around 10% for straight layouts and about 15% for diagonal or picture-frame patterns, which have more angled cuts.
Yes. Multiply the board, joist and screw counts by your local prices. Lumber prices change often, so the tool doesn't guess them.