How many deck boards do I need for a 12x16 deck?

With boards running the 16 foot way, 5-1/2 inch boards and 3/16 inch gaps cover 5-11/16 inches per row. 144 inches divided by 5.6875 is 25.3, so 26 rows of 16 foot boards: 26 boards.

How many joists for a 16 foot deck at 16 inches on center?

192 inches divided by 16 is 12 spaces, plus one joist to close the last space: 13 joists. At 12 inches on center it is 17, and at 24 inches it is 9.

Deck Calculator: Boards, Joists and Screws

Count

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Rim / band–

Ledger–

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Joist tape–

Deck area–

Estimate only: counts, not a design. No joist, beam, post or footing sizes or spans here. Most decks need a permit and inspection; for spans, footings and ledgers use DCA 6 or a licensed builder/engineer.

Plan

Decking and fasteners

Decking boards at Home Depot.
Deck screws and hidden deck fasteners.
Joist tape to protect joist tops.

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How the count works

Rows: deck width ÷ (board width + gap), rounded up. A 12' deck with 5-1/2" boards and 3/16" gaps: 144 ÷ 5.6875 = 25.3, so 26 rows. The last row is ripped to fit.

Boards per row: one board if the stock is at least as long as the deck. Otherwise boards are joined over a joist, so each board only counts the length that ends on a joist. "Best fit" picks the stock length that buys the fewest linear feet, then the fewest joints. Offcuts aren't reused in the count; stagger joints.

Joists: deck length ÷ spacing, rounded up, plus one (so the last, shorter space still ends on a joist). 16' at 16" on center: 192 ÷ 16 = 12, plus 1 = 13. Each joist is the deck width long. Rim and ledger each run the deck length.

Fasteners: face screws are 2 per board per joist (rows × joists × 2). Hidden clips are about 1 per board per joist; check the maker's count per box.

Questions

How many deck boards for a 12x16 deck?

26 sixteen-foot boards when they run the 16' way (5-1/2" boards, 3/16" gaps).

How many joists for a 16' deck at 16" on center?

13. At 12" on center it's 17; at 24" it's 9. Composite decking often needs 12" or 16" spacing, and less on diagonals: check the maker's install guide.

How many screws per deck board?

Two at every joist. 26 rows over 13 joists is 676 screws; buy a few percent extra.

Adding steps? Use the deck stairs calculator. For footing concrete, use a concrete calculator.

Safety

This counts materials; it doesn't size joists, beams, posts, footings or ledger connections. Ledger failures are a leading cause of deck collapses. Get a permit, follow DCA 6 or your local code, and consult a licensed builder or engineer.

Call 811 before digging footings.