Shiplap Wall Calculator
Board count and material from wall dimensions.
About this calculator
This calculator lays shiplap boards horizontally in rows: Board rows (courses) is Wall height (ft) converted to inches and divided by the Exposed width (ft) each board actually shows after overlap (Board width minus Overlap), rounded up. Wall height moves Board rows more than any other input, since it is the only dimension that determines how many horizontal rows are needed to cover the wall floor-to-ceiling. Wall width (ft), Board length (ft), Cost per board ($), and Waste factor (%) all have zero effect on Board rows -- rows are set purely by wall height and the exposed board width, before the horizontal board count per row or purchase math ever enters.
Openings to deduct (sq ft) only feeds Net wall area (sq ft), a display figure showing how much less wall is actually visible after subtracting windows and doors -- it does NOT reduce Boards to buy or Total coverage (sq ft), since full-length boards still need to span the wall width and get field-cut around any opening rather than being purchased shorter. Boards to buy multiplies Board rows by boards-per-row (Wall width divided by Board length, rounded up) and applies the Waste factor (%) on top, rounding up to a whole board at each step -- so even a small waste factor or a wall width just over a clean multiple of board length can push the purchased quantity up by a full extra board.
Inputs
Results
Board rows (courses)
20
How to Use This Calculator
- Enter Wall width (ft), Wall height (ft), and Board width (in).
- Set Overlap (in), Board length (ft), and Openings to deduct (sq ft).
- Adjust Cost per board ($), Waste factor (%) as needed.
- Review the Board rows (courses) result.
- Use Net wall area (sq ft) and Boards to buy to inform your decision.
How the result changes with Wall height (ft)
| Wall height (ft) | Board rows (courses) |
|---|---|
| 4 | 10 |
| 6 | 15 |
| 12 | 29 |
| 20 | 48 |
What each input means
- Wall width (ft)
- Width of the wall to cover with shiplap.
- Wall height (ft)
- Height of the wall.
- Board width (in)
- Nominal width of each shiplap board (common: 5.5 in for 1x6).
- Overlap (in)
- Overlap at each joint where boards interlock.
- Board length (ft)
- Length of each shiplap board.
- Openings to deduct (sq ft)
- Total area of windows and doors to subtract.
- Cost per board ($)
- Price per individual shiplap board.
- Waste factor (%)
- Extra boards for cuts and waste.
What each result means
- Net wall area (sq ft)
- Wall area minus openings.
- Board rows (courses)
- Number of horizontal rows of shiplap.
- Boards to buy
- Total boards including waste factor.
- Estimated nails
- Brad nails needed (2 per stud intersection at 16" OC).
- Total coverage (sq ft)
- Square footage of coverage from purchased boards.
- Board cost
- Estimated cost for shiplap boards.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersWall width (ft) = 12, Wall height (ft) = 8, Board width (in) = 5.5, Overlap (in) = 0.5 = 8 input(s) provided
- Calculate Board rowsBoard rows20 = 20
- Calculate Net wall areaNet wall area96 = 96
- Calculate Boards to buyBoards to buy44 = 44
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Does subtracting window and door area reduce the number of boards I need to buy?
No -- Openings to deduct (sq ft) only reduces Net wall area (sq ft), a display figure showing the visible wall area after subtracting openings. Boards to buy is based on the full wall width and height, since full-length shiplap boards still need to span across an opening and get field-cut around it rather than being purchased shorter for that row.
Why does wall height matter more than wall width for board rows?
Board rows (courses) is calculated purely from Wall height (ft) divided by each board's exposed width after overlap -- Wall width (ft) never enters that formula at all. Wall width only affects how many boards fit in each horizontal row (Boards to buy), a separate calculation from how many rows are needed vertically.
How does the overlap affect how much of each board actually shows?
Exposed Width (ft) is Board width (in) minus Overlap (in), converted to feet -- the portion of each board visible after the next board interlocks over it. A larger overlap reduces the exposed width per board, which can increase the number of rows needed to cover the same wall height, though the effect is masked at small overlap changes because Board rows is a rounded-up whole number.
Why might I need an extra board even with a modest waste factor?
Boards to buy rounds up at two separate steps: boards-per-row (Wall width divided by Board length) rounds up to a whole board, and the waste-adjusted total rounds up again. If your wall width sits just over a clean multiple of your board length, or your total with waste sits just over a whole-board boundary, you can end up purchasing a full additional board even for a small overage.
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