Shiplap Calculator
Calculate how many shiplap boards you need for your wall project.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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This calculator figures out exactly how many shiplap boards you need for any wall project, accounting for board overlap, openings, and waste. Here is how to get an accurate count:
- Enter your wall dimensions. Type the length and height of your wall in feet. The default height is 8 feet, which covers a standard residential ceiling. If you are covering multiple identical walls, increase the "Number of Walls" field instead of running the calculator multiple times.
- Subtract openings. Enter the number of doors and windows in the wall. The calculator deducts 21 square feet per door and 15 square feet per window, which matches standard residential rough openings. For non-standard sizes, adjust by adding or removing door/window counts to approximate the right deduction.
- Set your board dimensions. Standard shiplap is 1x6 lumber with an actual width of 5.5 inches. The overlap (rabbet or tongue depth) is typically 0.5 inches, leaving 5 inches of exposed face per board. If you are using a different profile, adjust these values to match.
- Set your waste factor. 10% is the standard buffer for cut waste, pattern starting offsets, and damaged boards. For rooms with many corners or diagonal installations, use 15%. For a simple single accent wall with straight horizontal runs, 5-7% may be enough.
- Read your results. The primary result is the board count to purchase. The breakdown shows total wall area, net area after openings with waste added, coverage per board, number of horizontal rows, and linear feet of trim needed for the perimeter and openings.
Results update instantly as you type. Use Share to send your inputs to a supplier or contractor, or Copy to paste the board count into a shopping list.
About the Shiplap Calculator
Shiplap is a horizontal board cladding where each plank overlaps the one below it by a small amount, typically 0.25 to 0.5 inches. This overlap, called a rabbet or reveal, serves two purposes: it keeps water out on exterior applications and creates the characteristic shadow line on interior accent walls.
The key measurement is the exposed face width, not the total board width. A 1x6 board (5.5 inches actual) with a 0.5-inch overlap exposes only 5 inches per row. To cover an 8-foot wall (96 inches), you need 96 / 5 = 19.2 rows, which rounds up to 20 rows. Each row uses as many boards as needed to span the wall length. Coverage per board equals the exposed width in feet multiplied by the board length.
The trim estimate covers the perimeter of your wall area plus the perimeter around each opening. This gives you a starting point for purchasing casing, baseboard, and corner trim, though trim layouts vary widely by design.
Frequently Asked Questions
How much shiplap do I need for a 12x8 foot wall?
A 12x8 foot wall (96 square feet) with standard 1x6 shiplap (5.5" wide, 0.5" overlap, 8-foot boards, 10% waste) requires approximately 26 boards. The exposed face width is 5 inches, giving 20 rows across the height. Each row needs 2 boards to span 12 feet, minus end trim cuts, but the calculator accounts for waste to cover partial boards at the ends of rows.
What is the standard overlap for shiplap?
Most interior shiplap uses a 0.25 to 0.5 inch overlap (the rabbet depth). A 0.5-inch overlap on a 5.5-inch board leaves a 5-inch exposed face, which is the most common profile. Some decorative profiles use a smaller 0.25-inch reveal for a tighter look. Exterior shiplap for weather resistance typically uses a larger 0.75 to 1-inch overlap. Always check the manufacturer's specification for the specific product you are using.
Should I use 1x6 or 1x8 shiplap boards?
1x6 boards (5.5 inches actual) are the most common choice for interior accent walls. They produce proportional shadow lines and are widely available as pre-primed shiplap or rough-sawn pine. 1x8 boards (7.25 inches actual) cover more area per board and suit larger walls or rooms with higher ceilings where the wider board looks more in scale. Wider boards also mean fewer rows and faster installation, but they are more prone to cupping and warping if the wood has not fully acclimated to the room's humidity.
Do I need to add a waste factor for shiplap?
Yes. Even on a simple rectangular wall, you will have cut-off pieces at the ends of rows that cannot always be reused, and occasionally a board will have a defect or be damaged during installation. A 10% waste factor is standard for straightforward horizontal installations. Increase this to 15% if you are running boards diagonally, doing a herringbone or chevron pattern, or working in a space with many outlets, light switches, or other cutouts. Buying a little extra upfront is much cheaper than a second trip to the hardware store to match the same lot of boards.