A 16 × 12 ft (4.88 × 3.66 m) deck needs 13 joists at 16 in (406 mm) centres and 26 rows of boards: 29 boards of 16 ft with 10% waste, held by about 676 screws.
Deck plan: joists dashed, boards across
계산 방법 S
Joists
⌈16in192in⌉+1=13joists of12ft
Rounded up, plus the joist at the far end. Rim joists and beams are extra.
Rows of boards
⌈5.5+0.125144in⌉=26
Rounded up; the last row may need ripping.
Boards
⌈1626×16×1.1⌉=29
Rounded up to whole boards.
Fasteners
26×13×2=676
Rule of thumb: two face screws, or one hidden clip, where each board crosses each joist.
Deck calculator 소개
Boards run along the house and joists run out from it. The joist count is the deck width divided by the joist spacing, rounded up, plus one for the far end. Rows of boards are the deck depth divided by board width plus gap, rounded up. Boards to buy are rows × deck width × (1 + waste) ÷ board length, rounded up, and fasteners are counted where each row crosses each joist.
The default 16 × 12 ft deck, with joists 16 in on centre and 5½ in boards gapped ⅛ in, needs 13 joists and 26 rows: 416 linear feet, or 29 sixteen-foot boards with 10% waste, held by 676 face screws.
Rim joists, beams, posts, ledger, blocking and stair stringers are not counted. Joist size and span depend on species, grade and load; take them from the span tables in 2021 or 2024 IRC section R507 or from AWC DCA 6.
계산 예제
16 × 12 ft deck, joists 16 in on centre, 5½ in boards, ⅛ in gap
16 in on centre suits 5/4 wood boards laid square to the joists. 2021 and 2024 IRC Table R507.7 allows 5/4 boards 16 in when each board crosses three or more joists (12 in over two), and 12 in when laid diagonally (8 in over two). 2x boards may span 24 in, except 18 in for diagonal boards over two joists. Composite boards use the span on their ASTM D7032 label.
How many deck boards do I need?
Divide the deck depth by the board width plus gap to get rows, then multiply by the deck width and add waste. For a 16 × 12 ft deck with 5½ in boards and ⅛ in gaps: 144 ÷ 5.625 = 25.6, so 26 rows; 26 × 16 ft = 416 linear feet; with 10% waste, 457.6 ft, or 29 boards 16 ft long.
How many screws do I need for a deck?
Two face screws wherever a board crosses a joist. A 16 × 12 ft deck at 16 in centres has 13 joists and 26 rows, so 26 × 13 × 2 = 676 screws, about 3.5 per square foot. Hidden clips take one per crossing, 338 here. Closer joist spacing adds crossings: at 12 in centres the same deck needs 884 screws.
How many joists do I need for a deck?
Divide the width along the house by the joist spacing, round up and add one. A 16 ft (192 in) deck at 16 in centres needs 192 ÷ 16 + 1 = 13 joists; at 12 in centres it needs 17, and at 24 in, 9. Rim joists, doubled joists under board splices and the beam are extra.
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정확도는 입력값과 계산 방법의 가정에 따라 달라집니다. 십진 연산은 유효숫자 50자리를 사용하지만, 추정값·수치해석 방법·원본 데이터의 정밀도는 더 낮을 수 있습니다. 표시값을 반올림해도 이러한 한계는 사라지지 않습니다. 독립적인 출처의 풀이와 대조한 계산 예시: 3. 예를 들어 “16 × 12 ft deck, joists 16 in on centre, 5½ in boards, ⅛ in gap”은 Python decimal: 192/16 + 1 = 13 joists; 144 ÷ 5.625 = 25.6 → 26 rows; 26 × 16 = 416 ft × 1.1 ÷ 16 = 28.6 → 29; 26 × 13 × 2 screws와 대조해 확인합니다.
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American Wood Council DCA 6 — Prescriptive Residential Wood Deck Construction Guide, based on the 2015 IRC (joist spacing 12, 16, 24 in); International Code Council — 2021 and 2024 IRC section R507 (exterior decks), Table R507.7 maximum joist spacing for decking.