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How Many Deck Boards for a 12 x 16 Deck?

A 12 x 16 foot deck laid with 5-1/2 inch boards and 1/8 inch gaps needs 26 boards (29 with 10% for waste), 13 joists at 16 inch spacing and about 676 screws.

Try your own numbers

Deck length (boards run this way)Deck widthJoist spacing (centre to centre)Board widthGapClose-up
Key Boards run the length of the deck, across the joists.
Units
ft
ft
Typical board. A 5/4 x 6 deck board is about 5.5 in wide. Use the width of the board you are buying. Editorial rule of thumb.
in
in
Set lengths. Boards are sold in set lengths, so check your supplier’s list. The starting figure just matches the deck.
ft
in

Follow your board maker’s guide.

%
Board rows across the deck26 rows of 1 board
Boards, no waste26
Boards to buy, with waste29 boards
Joists13 × 12 ft
Screws676

Boards run along the 16 ft length, across joists that run along the 12 ft width. Rows: (12 ft + gap) ÷ (5.5 in board + gap) = 25.62, rounded up to 26. Joists: 16 ÷ 16 in spacing, rounded up, plus one = 13. Screws: 26 × 13 × 2 = 676.

Check the joist spacing against your board manufacturer’s guide and local rules.

Fig. 1 A 12 x 16 ft deck, boards along the 16 ft length.

Every formula is tested against worked examples. How we check

Joist spacingJoistsScrews
12 in17884
16 in13676
18 in12624
24 in9468

Fig. 2 The same deck at different joist spacings.

Last checked 11/10/2026. Sources: Olathe, Kansas: deck guidelines reproducing the IRC decking table (1¼ in boards 16 in on centre across joists).

How the 26 comes out

The boards run along the 16 ft length, so they cross joists that run along the 12 ft width. Each row of board plus gap is 5.625 in wide, and 144.125 in (the width plus one gap) ÷ 5.625 = 25.6, which rounds up to 26 rows. With 16 ft boards, each row is one board.

Joists are 16 in apart along the 16 ft length: 192 ÷ 16 = 12 spaces, so 13 joists. Two screws at each of the 26 × 13 crossings is 676 screws.

Does the board length matter? Yes. If you buy 8 ft boards each row is two boards, so you need 52, and the butt joints must land on a joist. Choose the board length that fits the deck and leaves the least offcut.

Common questions

Do I need 16 inch joist spacing?

16 in on centre is the figure for 1-1/4 in decking laid across the joists in the IRC table, as reproduced in a Kansas city guide. Composite and diagonal layouts often need closer joists, so follow your board’s instructions.

Does this include the frame?

Only the joists. Posts, beams, ledger and railings are outside this calculator and need local advice.

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