Shiplap is priced and installed by the linear foot, but most people start with a wall's width and height. This calculator bridges that gap: it converts your wall dimensions, board size, and reveal into the number of rows, total linear feet, and (if you tell it your stock length) the number of boards to buy.
How the Shiplap Calculator works
The calculator treats the reveal — the exposed face of each installed board — as the coverage width per row. Dividing the wall's height by the reveal gives the number of rows, rounded up since a partial row still consumes a full board's height. Multiplying rows by the wall's width gives the raw linear footage, and adding your waste percentage accounts for cut ends, culled boards, and mistakes.
Inputs and what they mean
Wall width and height are in feet. Board width is the nominal size (1x4 through 1x12) with its actual dressed width filled in automatically. Reveal is the one input worth double-checking: it's the visible face after the lap joint overlap, not the full nominal board width — check your specific shiplap profile's spec sheet if you're unsure. Waste allowance defaults to 10%, a reasonable starting point for a straightforward wall.
Limits and edge cases
This calculator assumes a single flat wall with no deductions for windows or doors — for a wall with large openings, measure the openings separately and subtract their area from your total before ordering, or simply rely on the waste allowance to absorb the extra cutting. For vertical shiplap, swap the wall width and height values, since each board then spans the wall's height instead of its width.