Shiplap Calculator
This shiplap calculator turns wall length and height into boards, linear feet and rows using the real face coverage of each profile, with the final ripped row called out.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Boards
- 42 boards
- 1x6 at 8 ft, each covering 3.42 sq ft, for 128 sq ft of wall plus 10% waste
- Rows up the wall
- 19 rows
- 18 full at 5.13 in of face plus a last piece ripped to 3.75 in. Plan that rip where it is least seen, which is usually behind the baseboard or above a cabinet run
- Linear feet to buy
- 336 ft
- 42 boards at 8 ft. Only about 300 ft lands on the wall, and the rest is cut, cull and end trim
- Coverage ordered
- 140.8 sq ft
- 128 sq ft of wall less 0 sq ft of openings, carried at 10% waste
- Fasteners
- 450 nails
- Two 2 in 18 gauge brads at every crossing of studs or furring 16 in apart. Shiplap has to land on framing, not on drywall alone. Add about 10 tubes of adhesive if the wall is out of plane
Shiplap formula
Sq ft per board = face coverage (in) / 12 x board length (ft)
Boards = (wall area - openings) x (1 + waste %) / sq ft per board, rounded up
Rows = wall height (in) / face coverage, with the remainder ripped into the last row
Nails = installed linear ft x 12 / 16 x 2Worked example
A 12 ft wide by 9 ft tall chimney wall in 1x8 shiplap, 7-1/8 in of face, 12 ft boards, one 15 sq ft window and 10 percent waste. The wall is 108 sq ft, less 15, is 93 sq ft net, or 102.3 with waste. Each 12 ft board covers 7.125 / 12 x 12 = 7.125 sq ft, so 102.3 / 7.125 = 14.4, rounded up to 15 boards and 180 linear feet.
Rows: 108 in of height divided by 7.125 in of face is 15.16, so 15 full rows and a top piece ripped to 1-1/8 in. That last strip has no rabbet left to hold it, so drop the bottom course an inch and let the baseboard cover it, which puts the top rip at 2-1/8 in. Installed length is 93 / 0.59375 = 156.6 ft, so 118 framing crossings and about 236 brads.
Quick reference
| Profile | Board length | Face coverage | Sq ft per board | Boards per 100 sq ft |
|---|---|---|---|---|
| 1x4 | 8 ft | 3-1/8 in | 2.08 | 53 |
| 1x6 | 8 ft | 5-1/8 in | 3.42 | 33 |
| 1x6 | 12 ft | 5-1/8 in | 5.13 | 22 |
| 1x8 | 8 ft | 7-1/8 in | 4.75 | 24 |
| 1x8 | 12 ft | 7-1/8 in | 7.13 | 16 |
| Cedar lap 1x6 | 8 ft | 4-3/4 in | 3.17 | 35 |
Coverage, not nominal width, sets the board count
Shiplap is rabbeted on both long edges so each board laps the one beside it. That lap is hidden, so a 1x6 that measures 5-1/2 in wide only shows about 5-1/8 in on the wall, and a 1x8 shows about 7-1/8 in. Use the face coverage the mill publishes; guessing off the nominal size undercounts by roughly 7 percent, which is a missing board on every fifteenth. Exterior cedar lap from the same nominal 1x6 shows only 4-3/4 in because the lap is deeper.
This is where shiplap parts company with board and batten. Board and batten is flat stock, usually sheet goods or wide boards, with narrow battens nailed over the seams, so the layout question is where the battens land. Shiplap has the joint milled into the board, so the only layout question is where the rows fall. Nickel gap is shiplap with a 1/8 in reveal built into the profile; a plain rabbeted shiplap closes tight and reads as a thin line.
Acclimate, find the framing, then set the first row
Stack the boards in the room with stickers between them for at least 72 hours, longer in winter when a heated house runs dry. Wood moves across the grain, and boards installed at lumberyard moisture content shrink and open every joint. Prime or first-coat all four sides before install, including the rabbets, so shrinkage does not expose a stripe of raw wood in every reveal.
Shiplap has to reach framing. Mark every stud, or screw 1x3 furring across the wall at 16 in on center for vertical boards. Two 2 in 18 gauge brads per crossing is the pattern, one through the rabbet and one near the bottom edge. Level the first course with a laser rather than the floor and scribe the bottom edge to whatever the floor is doing, because an eighth of an inch of error at the base compounds into a visible slope by the ceiling.
What this calculator leaves out
Furring strips, blocking and the shims a wavy wall needs to come flat. Inside and outside corner trim, the scribe pieces where the run meets a window or a door casing, and any picture rail or crown that caps it. Primer and finish coats, filler for the brad holes, and the caulk at the perimeter. It also skips the cost of ripping down the last row on a table saw and the extra board most people buy so a split or a cupped piece does not stop the job.
Mistakes that cost money
- Boards fastened to drywall alone pull off within a season; hit studs or add 1x3 furring at 16 in on center.
- Installing boards straight off the truck: they shrink across the grain and every joint opens by spring.
- Starting the first course off a floor that is out of level, so the rows visibly tilt by the top of the wall.
- 16 gauge nails through the face of a 1/2 in board split it; use 18 gauge brads or predrill near the ends.
- Butt joints landing between studs. They cup and open, so plan every joint on framing and stagger by two rows.
- Painting only after install, which leaves raw wood showing in the reveals as the boards shrink.
Key facts
- A nominal 1x6 shiplap board measures 5-1/2 in wide and shows about 5-1/8 in of face once the rabbets lap.
- The Western Red Cedar Lumber Association lists green lap siding from a nominal 1x6 as dressed to 5-1/2 in with a 4-3/4 in exposed face.
- Nickel gap shiplap carries a 1/8 in reveal milled into the profile; a plain rabbeted shiplap closes with no visible gap.
- Shiplap is rabbeted on both edges so each board laps the one below it, where board and batten is flat stock with narrow battens covering the seams.
- Solid wood paneling needs at least 72 hours stacked in the room it will be installed in, and longer in winter when indoor humidity drops.
Frequently asked questions
How many boards do I need for a shiplap wall?
Divide the net wall area by the square feet one board covers, then add waste. A 16 x 8 ft wall is 128 sq ft; a 1x6 board 8 ft long covers 3.42 sq ft, so 128 x 1.10 / 3.42 is 42 boards and 336 linear feet.
What is the difference between shiplap and board and batten?
Shiplap boards are rabbeted on both edges so they interlock and the joint is part of the board. Board and batten is flat stock with narrow battens nailed over the seams. One is a board count, the other is a batten layout.
Does shiplap have to be nailed into studs?
Yes. Brads into drywall alone let the boards work loose as they move. Mark the studs, or screw 1x3 furring across the wall at 16 in on center, which also gives vertical boards something to land on.
What is nickel gap shiplap?
A shiplap profile with a 1/8 in reveal milled into the rabbet, so the boards self-space and every joint line comes out the same. A plain rabbeted shiplap closes tight instead, which reads as a hairline and shows any shrinkage.
Sources and references
- Western Red Cedar lap and channel siding: coverage table and pattern numbers (Western Red Cedar Lumber Association)
- Shiplap and pattern paneling profiles for interiors (UFP Edge)
- Indoor tongue and groove paneling: preparation and finishing (Western Red Cedar Lumber Association)
Next steps for this project
The usual order for a paint & walls project. See all paint & walls calculators.
Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.