A 12 by 8 foot shiplap accent wall in 1x6 boards, which show a 4½ inch face, laid with a ⅛ inch gap, takes 21 rows and 252 linear feet of shiplap: 35 boards 8 feet long with 10% extra, and 420 nails at two per stud in every row. The top row is ripped down to 3½ inches.
How the shiplap calculator works
Shiplap is counted in rows, not square feet, because each board covers only its exposed face plus the gap. The lap that the next board hides does not count.
Rows = wall height ÷ (face width + gap), rounded up
Linear feet = rows × wall width − opening area ÷ (face width + gap)
Boards are the linear feet plus waste divided by the board length, rounded up. Doors and windows come off by area (21 and 12 square feet each). Nails are two per stud in every row, following Bob Vila's "two 2-inch nails in every wall stud", reduced by the share of the wall that openings take up.
Worked example: a 12 × 8 ft wall
| Step | Numbers | Result |
|---|---|---|
| Exposure | 4½ in face + ⅛ in gap | 4⅝ in |
| Rows | 96 in ÷ 4⅝ in = 20.8, rounded up | 21 rows |
| Linear length | 21 × 12 ft | 252 ft |
| Boards | 252 × 1.10 ÷ 8 ft = 34.7 | 35 boards |
| Studs crossed | 12 ft ÷ 16 in + 1 | 10 per row |
| Nails | 21 × 10 × 2 | 420 nails |
The 21st row only needs 3½ inches (96 − 20 × 4⅝), so rip one board lengthwise for the top. In 12 foot lengths the same wall takes 24 boards, with fewer joints to stagger.
Face width versus board width
A 1x6 is 5½ inches wide, but it does not cover 5½ inches of wall. The Western Red Cedar Lumber Association's coverage table gives these exposed faces for lapped boards:
| Nominal | Dressed width | Exposed face |
|---|---|---|
| 1x6 | 5½ in | 4½ in |
| 1x8 | 7½ in | 6½ in |
| 1x10 | 9½ in | 8½ in |
Store-bought pine and MDF shiplap is milled with laps of different depths, so the face can differ from these. Measure one board from the face edge to where the lap starts, and choose "Other" to type it in. With 1x8 boards (6½ inch face) the example wall drops to 15 rows, 180 feet and 25 boards.
Shiplap from plywood
Ripping plywood into strips is the budget version. Bob Vila rips strips 5⅞ inches wide, eight 8 foot strips per sheet, and spaces them ⅛ inch apart. Strips have no lap, so the whole width shows: pick "Plywood strips" and the exposure becomes 6 inches.
Gaps, spacers and nails
The small shadow line between boards is the look most people want. Bob Vila uses a ⅛ inch gap; a nickel is a common spacer for that. Set the gap to 0 for tight-fitting boards. The calculator lists a handful of spacers, since you move them along each row.
Nail every stud (or ceiling joist) in every row, two nails each, 2 inches long, into the framing. Choose 16 or 24 inch framing to match your wall; the dashed lines on the drawing show where the nails go.
Shiplap on a ceiling
On a ceiling the boards run the long way, across the joists. A 14 by 12 foot ceiling in 1x6 has 32 rows 14 feet long: 448 linear feet, 62 boards of 8 feet and 704 nails at two per joist, 16 inches apart. On ceilings it pays to buy boards long enough to span the room, or to land every joint on a joist.
Doors, windows and waste
Openings are subtracted by area, so a 3 by 4 foot window on the example wall saves 12 square feet divided by the 4⅝ inch exposure, about 31 linear feet. Keep the 10% waste, or go to 15% on a wall with several openings, because the offcuts around a window are rarely long enough to reuse.
Next steps
- Vertical boards with battens instead: the board and batten calculator.
- Shiplap only up to chair height: the wainscoting calculator sets the height.
- Ripping strips from sheets: the plywood calculator counts sheets.
- Locate the framing first with the stud calculator.
- Painting it white after: the paint calculator.
More wall coverings are listed in drywall, paint and walls.