Board and batten layout math
Board and batten siding alternates wide boards with narrow battens that cover the gaps between boards. The repeat module is one board width plus one gap (or one batten width). The number of boards across a wall equals the wall width divided by the module width, rounded up.
Battens are one fewer than boards for an open-end layout, or equal to the board count for a wall that wraps battens at both edges. Board length equals the wall height, and waste should include 10 percent for cuts around windows and doors.
Boards = ceil(Wall width / (Board width + Gap))
Each board-plus-gap unit defines one repeat module across the wall face.