Deck Boards Calculator

How many deck boards, linear feet and screws you need for a rectangular deck, from board width, gap, board length and joist spacing.

2×6 and 5/4×6 boards are 5½ in wide; 2×4 is 3½ in.
AWC DCA 6 says to space boards about ⅛ in apart; follow the maker’s spec for composites.
Used for the screw count (2 fasteners per board at every joist).
%
$per board
Your rate is remembered on this device.
16 ft boards (incl. waste)
29 boards
Rows of boards across the deck
26
Linear length of decking (net)
416
Deck screws (approx.)
676 screws
Deck area
192
Estimated decking cost
$435.00
Decking only: excludes framing, fasteners, railings and stairs.

Estimate generated with SortedSums: https://sortedsums.com/deck-boards-calculator/. For informational purposes only; verify before relying on it.

Estimate only. This tool is for informational and educational purposes. Results depend on your inputs and simplifying assumptions, and are not a substitute for professional engineering, design or financial advice. Always verify with a qualified professional and applicable codes before purchasing, building or making decisions.

How it’s calculated

Rows = ⌈ (deck width + gap) ÷ (board width + gap) ⌉ Linear feet = rows × deck length Boards = ⌈ linear feet × (1 + waste%) ÷ board length ⌉ (but never fewer than it takes to cut every row) Screws ≈ rows × joists × 2

Example: a 16 ft × 12 ft deck with 5½ in boards and ⅛ in gaps: 144 in ÷ 5.625 in = 25.6 → 26 rows. 26 × 16 ft = 416 linear ft; with 10% waste 457.6 ft ÷ 16 ft = 29 boards. Joists at 16 in: 13 joists, so about 26 × 13 × 2 = 676 screws.

Choose board lengths that let butt joints land on joists, and stagger joints between rows. Each piece should bear on at least 3 joists (AWC DCA 6).

Offcuts only help if they are long enough for another row. On a 12 ft deck, 16 ft boards leave 4 ft offcuts, so each of the 26 rows still uses a whole board: 26 boards, not the 22 that linear feet alone would suggest. Matching board length to deck length saves money.

Frequently asked questions

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

With boards running the 16 ft way, 5½ in boards and ⅛ in gaps give 26 rows of 16 ft boards, or 29 boards with 10% waste.

How much gap between deck boards?

The AWC prescriptive deck guide (DCA 6) calls for about ⅛ in between wood boards. Wet pressure-treated boards are often butted tight because they shrink as they dry; composites have their own spacing rules.

What length deck boards should I buy?

Pick a length that equals the deck length or divides it with little left over (e.g. 12 ft boards for a 12 ft or 24 ft deck). Offcuts shorter than a row are mostly waste, and every piece should span at least 3 joists.

How many screws per deck board?

Two at every joist the board crosses. With 5½ in boards on joists 16 in apart that works out to about 3½ screws per square foot of deck.

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Sources

Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.

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