Deck Boards Calculator: 28 Boards for a 16x12 ft Deck

What does deck boards needed 28 boards mean?

It means twenty-eight boards deck a 16 ft by 12 ft deck, with room for cuts. The deck is 12 ft wide across the boards, which is 144 inches; one board plus its gap, the pitch, is 5.75 inches, so the exact need is 144 divided by 5.75, or 25.04 boards, and with 10% waste for end cuts and bad boards that becomes 27.55, rounded up to 28 whole boards because boards are sold by the board, not by the fraction. Each board is 16 ft long, the length of the deck, so the order is 28 boards at 16 ft. The spare boards are not spare stock exactly — they are the boards the end cuts, the stair notch and the one split board consume, so a deck boarded to the exact count runs short before the last row.

Output · formula · meaning

Three things to check before you trust the number

First, check which way the boards run: this calculator counts boards laid across the width, each as long as the deck is long. If your boards run the other way, swap length and width and the count follows the new width. Second, remember the count follows the width, not the area: a 16 ft by 12 ft deck is 192 sq ft, but the boards are counted by the 12 ft width divided by the pitch, and a deck measured by its area over-orders or under-orders depending on the board. Third, judge the gap honestly: a quarter inch is the common gap, but a deck boarded tight in winter swells shut in summer, and a half inch gap drops this deck to 27 boards. Framing, screws and stain are bought separately — see the deck stain calculator for the finish on the same deck.

Worked example

16 ft long, 12 ft wide, 5.5 in boards, 0.25 in gap, 10% waste. Width in inches: 12 × 12 = 144 in. Board pitch: 5.5 + 0.25 = 5.75 in. Boards exact: 144 ÷ 5.75 = 25.04. With waste: 25.04 × 1.10 = 27.55, rounded up to 28 boards, each 16 ft long. In practice that means buying 28 boards at 16 ft, and expecting the last ones to go on end cuts and the stair notch. If the same deck were 14 ft wide instead, the need would rise to 33 boards, but the deck boarded would be identical in length.

Every branch, checked

With a 14 ft wide deck instead of 12 ft, the width rises to 168 in and the need to 33 boards. With a 20 ft long deck, the need stays 28 boards, but every board must be 20 ft long instead of 16 ft, since length sets the board length, not the count. With a 0.5 in gap, the pitch rises to 6 in and the need falls to 27 boards. With 5% waste, the exact need stays 25.04 boards but the buy falls to 27 boards, since 25.04 × 1.05 is 26.29 and still rounds up to 27. Deck width, board width, gap and waste each move the order on their own, so a wrong gap figure is as costly as a wrong measurement.

The reverses, worked backwards

The width behind 28 boards is 12 ft: at 10 ft the need is 23 boards (16 ft × 10 ft deck, 5.5 in boards, 0.25 in gap, 20.87 boards exact, 10% waste); at 14 ft it is 33 boards (16 ft × 14 ft deck, 5.5 in boards, 0.25 in gap, 29.22 boards exact, 10% waste). The board width behind 28 boards is 5.5 in: at 4.5 in the need is 34 boards (16 ft × 12 ft deck, 4.5 in boards, 0.25 in gap, 30.32 boards exact, 10% waste); at 7.25 in it is 22 boards (16 ft × 12 ft deck, 7.25 in boards, 0.25 in gap, 19.2 boards exact, 10% waste). The waste behind 28 boards is 10%: at 0% the need is 26 boards (16 ft × 12 ft deck, 5.5 in boards, 0.25 in gap, 25.04 boards exact, 0% waste); at 15% it is 29 boards (16 ft × 12 ft deck, 5.5 in boards, 0.25 in gap, 25.04 boards exact, 15% waste). Each reverse moves one input and holds the rest, so the step is exactly one width, board or waste change.

What the defaults assume

The defaults assume a 16 ft by 12 ft rectangular deck, boards laid across the width, 5.5 in boards with a 0.25 in gap, and 10% waste for cuts and bad boards. They do not assume framing, screws, railing or stain — a deck with stairs counts its stair boards separately, and the finish is bought by the gallon, not by the board.

Who uses this

• A homeowner decking a backyard: the 28-board order settles the yard call before the first board is cut.
• A DIY builder replacing deck boards: the same maths on the deck alone gives the boards, not a whole house.
• A contractor quoting a job: deck width, board width, gap, waste — the quote follows the same four steps, and the gap line shows the client why.
• A landlord budgeting a deck refit: the deck width off the plans, divided by the pitch, gives the board line on the refit budget.

Accuracy & limitations

The arithmetic is exact for the inputs entered; the judgement is the board direction and the gap. Real decks have stairs, notches and picture-frame borders, and the board on the pallet overrides any planning figure; a deck measured by its area over-orders, and a gap read off a dry deck under-orders one boarded in the wet season. Treat 28 boards as the planning order for a 16 ft by 12 ft deck at 5.5 in boards, a 0.25 in gap and 10% waste, and allow 15% for a deck cut with stairs and notches.

Cite this calculator

Bright Side Kit, “Deck Boards Calculator: 28 Boards for a 16x12 ft Deck”, https://brightoolbox.com/deck-boards-calculator/, accessed 3 November 2026. Students and researchers: cite the calculator name, the page URL and the date you used it, and quote the defaults (16 ft × 12 ft deck, 5.5 in boards, 0.25 in gap, 10% waste) so the 28-board result can be checked.

Frequently asked questions