How it works
The calculator divides the area to cover by the area one board actually covers on the wall – its exposed face times its length – after adding the waste allowance.
Net area = Wall length × Height − Windows and doors
Exposed face = Coverage per board ÷ Board length or your face width
Running length = Net area × (1 + Waste ÷ 100) ÷ Exposed face
Boards = ⌈ Running length ÷ Board length ⌉ · Rows = ⌈ Height ÷ Exposed face ⌉
Nails = ⌈ Running length ÷ Stud spacing ⌉ × Nails per stud
⌈ ⌉ rounds up to a whole number.
Worked example in words
A 12 × 8 ft accent wall is 96 sq ft. With 10 % extra that is 105.6 sq ft. A 12 ft board of 1 × 6 pine shiplap covers 4.94 sq ft, so 105.6 ÷ 4.94 = 21.4 means 22 boards. The face is 4.94 sq ft ÷ 12 ft = 4.94 in, so the 96 in wall takes 20 rows, and the boards add up to about 257 ft of running length.
Exposed face, not nominal width
Shiplap is sold by nominal size, such as 1 × 6, but each board overlaps the next one, so it covers less than its width. The Great American Spaces sell sheet gives the coverage directly: 4.94 sq ft per 12 ft board and 6.59 sq ft per 16 ft board, both about 4.94 in of face. For other boards, measure the face that shows once two boards are fitted together, or use the coverage on the label.
Shiplap or wainscoting
This calculator covers whole walls and ceilings. For panels or planks on the lower part of a wall with a cap or chair rail, use the wainscoting calculator.
Worked example
Inputs
- Measure by
- Wall length × height
- Wall length
- 12 ft
- Wall height
- 8 ft
- Boards
- 1 × 6 pine shiplap, 12 ft (4.94 sq ft per board)
- Waste allowance
- 10 %
- Stud spacing
- 16 in
Result
- Area to cover
- 96 sq ft
- Exposed face width used
- 4.94 in
- Rows of boards up the wall
- 20
- Running length of boards
- 256.5 ft
- Boards to buy
- 22
Common mistakes
- Dividing by the nominal width. The 1 × 6 pine shiplap here covers about 4.94 in of wall, not 6 in, so a calculation with 6 in comes up nearly a fifth short.
- Forgetting the waste allowance. Ends, cuts around windows and boards with knots you do not want add up; the maker of the example boards recommends at least 10 % extra.
- Buying boards from different batches. Color varies from lot to lot, so buy the whole job at once.
- Not leaving a gap at the ceiling and corners. Wood moves with humidity, so the first and last boards are trimmed, which uses some of the extra.
- Nailing only into drywall. Shiplap is fastened into studs, so mark them before you start.
Assumptions and limits
- The count is based on area, using the face each board covers. Real use depends on how well offcuts can be used on other rows.
- Boards run horizontally; vertical boards are counted the same way.
- Windows and doors are subtracted as rectangles; the trim around them is not included.
- Nails, if counted, are one set per stud crossing along the whole running length.
- Primer, paint, adhesive and trim are not included.
Frequently asked questions
How do I calculate how much shiplap I need?
Multiply the wall length by its height, subtract windows and doors, and add your waste allowance. Then divide by the area one board covers – its exposed face times its length. A 12 × 8 ft wall is 96 sq ft; with 10 % extra that is 105.6 sq ft, and with 12 ft pine boards covering 4.94 sq ft each you need 22 boards.
How wide is a 1 × 6 shiplap board?
A nominal 1 × 6 board is narrower than 6 in, and part of it hides under the next board. The Great American Spaces 1 × 6 pine shiplap covers 4.94 sq ft per 12 ft board, or about 4.94 in of wall per board.
How many shiplap rows go on an 8 ft wall?
Divide the height by the exposed face. 96 in ÷ 4.94 in is 19.4, so 20 rows, with the top row trimmed to fit.
Is shiplap the same as wainscoting?
No. Wainscoting covers the lower part of the wall with panels or planks and a cap; shiplap usually covers the whole wall or ceiling with horizontal boards. Use the wainscoting calculator for a partial-height wall.
How much extra shiplap should I buy?
Great American Spaces recommends at least 10 % extra for waste and trimming, and buying the whole job at once so the color matches. Rooms with many windows or angles may need more.
Sources
- ShipLap Collection sell sheet (03.22) — Great American Spaces (hosted by Lumbermens). Solid pine shiplap, 1 in × 6 in nominal, 1/8 in nickel gap; coverage "4.94 sq ft per 12' board", "6.59 sq ft per 16' board" (≈ 4.94 in of face per board); "(square footage to cover + 10% for waste/trim)" and "plus a minimum of 10% overage". Waste default 10 %.
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 6, 2026