Shiplap Calculator
Enter a wall's size, board width, and overlap and get the linear feet and number of shiplap boards to buy — waste allowance built in.
boards = 528 ft ÷ 12 ft → 44 boards
Shiplap boards overlap. Each board has a rabbet — a notch — along its edges that tucks behind the next board, so the face you actually see is narrower than the board's full width. A nominal `1×6` measures about `5.5 in` wide but exposes closer to `5 in` once the `0.5 in` lap is hidden. That exposed width, not the full width, is what covers the wall, so it drives every number.
To find how much board to buy, divide the wall area by the exposed coverage width. Area divided by a width gives a length — the linear feet of board needed to clad the wall. Add a waste allowance for the cuts at corners, windows, and the ends of each run, then, if you are buying fixed lengths, divide by the board length and round up to get a piece count. A tighter lap or a wider board covers more per foot and drops the total.
Enter the wall's length and height, choose your board width, overlap, board length, and a waste percentage. The tool returns the exposed coverage width, the linear feet of shiplap, and the number of boards. It counts a plain rectangular wall by area — subtract large openings and add for an accent wall's returns as your layout requires.
coverage width = 5.5 − 0.5 = 5 in → 200 sq ft ÷ (5/12 ft) = 480 lin ft
with waste = 480 × 1.10 = 528 lin ft → 528 ÷ 12 = 44 boards