Shiplap Calculator — Boards for a Wall or Ceiling
Shiplap boards overlap, so a 5 1/2 inch board covers about 5 inches of wall. Enter the area and this gives you the boards, the rows and the nails — using the exposed face, not the board width.
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How to work it out
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Measure the wall
Length times height. For an accent wall that is one rectangle; for a whole room add a section for each wall and the calculator totals them.
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Use the exposed face, not the board width
A 1 × 6 shiplap board measures 5 1/2 inches wide, but the rabbet on the edge tucks under the next board. What you see — and what it covers — is about 5 inches. Calculate on 5 1/2 and you will be roughly ten per cent short.
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Work out the rows
Wall height in inches divided by the exposure. A nine foot wall in 5 inch shiplap is 108 ÷ 5 = 21.6 rows, so twenty-two with the last one ripped narrow. Decide now whether the narrow row goes at the top, at the bottom, or gets split between both.
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Order full lengths where you can
A run of boards with no joins looks far better than one with butt joints scattered across it. If the wall is twelve feet, buy twelve foot boards rather than joining two eights. Where joins are unavoidable, stagger them and land every one on a stud.
What one board covers
Coverage is the exposed face.
| Board | Actual width | Exposed | 8 ft board | 12 ft board |
|---|---|---|---|---|
| 1 × 4 shiplap | 3 1/2 in. | 3 1/8 in. | 2.08 sq ft | 3.13 sq ft |
| 1 × 6 shiplap | 5 1/2 in. | 5 in. | 3.33 sq ft | 5.00 sq ft |
| 1 × 6 nickel gap | 5 1/2 in. | 5 1/8 in. | 3.42 sq ft | 5.13 sq ft |
| 1 × 8 shiplap | 7 1/4 in. | 6 7/8 in. | 4.58 sq ft | 6.88 sq ft |
| 1 × 8 T&G | 7 1/4 in. | 7 in. | 4.67 sq ft | 7.00 sq ft |
Exposure × length ÷ 12. The lapped or tongued edge does no covering.
Boards for a common accent wall
1 × 6 shiplap at 5 in. exposure, 10% waste, 8 ft boards.
| Wall | Area | Boards | Rows at 9 ft |
|---|---|---|---|
| 8 × 8 ft | 64 sq ft | 22 | 20 |
| 10 × 9 ft | 90 sq ft | 30 | 22 |
| 12 × 9 ft | 108 sq ft | 36 | 22 |
| 14 × 9 ft | 126 sq ft | 42 | 22 |
| 16 × 10 ft | 160 sq ft | 53 | 24 |
Rows depend only on height and exposure, not on wall length.
How much wall does a shiplap board cover?
Less than its width, always. A 1 × 6 shiplap board is 5 1/2 inches across, but the rabbeted edge slides under its neighbor, so about 5 inches of it is visible. An eight foot board therefore covers 3.33 square feet, not the 3.67 the board itself measures.
That gap is roughly nine per cent, which on a whole room is several boards. It is the single most common reason a shiplap order comes up short.
Shiplap, nickel gap and tongue and groove
Shiplap has a rabbet cut in opposite edges so boards overlap. Traditional shiplap closes tight; the fashionable version leaves a deliberate shadow line. Nickel gap is shiplap milled so the gap is a consistent eighth of an inch — the thickness of a nickel — without you having to space it.
Tongue and groove interlocks rather than overlapping and closes tight with no shadow line, which reads as more traditional panelling. All three calculate the same way: coverage is the exposed face.
Where the narrow row goes
The last row is almost never a full board. On a nine foot wall in five inch shiplap you get twenty-one full rows and a three inch strip left over.
Putting it at the top hides it behind crown or in shadow. Putting it at the bottom hides it behind baseboard. Splitting the difference — ripping both the first and last row so they match — looks deliberate and is what a trim carpenter would do. What you should not do is leave a two inch sliver at eye level.
Find the studs before you start
Shiplap has to be nailed into framing, not just into drywall. Mark every stud floor to ceiling before the first board goes up, because once boards start covering the wall you are guessing.
Two brads per stud crossing, angled slightly, near the top edge where the next board will hide them. Construction adhesive on the back as well if the wall is staying put permanently.
Let it acclimate first
Wood moves with humidity, and boards installed straight off the truck will shrink once they adjust to the room. On tight-fitting tongue and groove that opens gaps; on shiplap it widens the shadow line unevenly.
Stack it in the room it is going in, with spacers between the boards so air gets around them, and leave it three or four days. It is a dull step that prevents a visible problem.
How this is worked out
No black box — here is the arithmetic the calculator runs, so you can check it against your own numbers.
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coverage per board = (exposed face in. ÷ 12) × board length ftThe lapped edge is hidden and covers nothing. -
boards = (area − openings) × (1 + waste) ÷ coverage per boardRounded up. Boards are sold whole. -
rows = wall height in. ÷ exposed face in.Rarely whole, which is why the last row gets ripped. -
linear feet = boards × board lengthUseful when the supplier prices by the linear foot rather than the piece.
Common questions
How many shiplap boards do I need?
Divide the wall area by what one board covers — exposure divided by twelve, times the board length. A 12 × 9 ft wall in 1 × 6 shiplap with 8 ft boards takes about 36 boards with ten per cent waste.
How much does a 1 × 6 shiplap board cover?
About 5 inches of wall, not 5 1/2. An 8 ft board covers 3.33 sq ft and a 12 ft board covers 5. The difference between the board width and the exposed face is the lap, and it covers nothing.
What is nickel gap?
Shiplap milled so that the rabbet leaves a consistent 1/8 inch gap between boards — about the thickness of a nickel. It gives you the shadow line without spacing every board by hand.
Should shiplap run horizontally or vertically?
Horizontal is the common look and makes a room feel wider. Vertical draws the eye up and suits a tall narrow space. Vertical needs blocking or furring between the studs to nail into, since there is no framing running the right way.
Do I need to remove the drywall first?
No — shiplap goes straight over drywall, and the drywall gives you a solid backing. Just remember it builds the wall out by three-quarters of an inch, so outlets need extenders and door casing may need packing out to suit.
How much waste should I allow?
Ten per cent on a plain wall. Fifteen if you are cutting around windows and doors, or if the room is small enough that cut-offs have nowhere to be used up.
Can I use shiplap in a bathroom?
Yes, away from direct water. Prime all six faces before it goes up, including the back and the ends, and run a bead of caulk where it meets the tub or counter. Inside a shower enclosure it is a bad idea whatever it is primed with.
Should I paint before or after installing?
Prime and paint the boards before they go up, then fill the nail holes and do a final coat on the wall. Trying to cut in along every shadow line after the fact is slow and never looks as clean.
Where these figures come from
Every figure below is traceable. How we check the numbers explains how they are verified, and the coverage reference collects them all in one place.
- Manufacturer product data — actual widths and stated coverage per board
- American Softwood Lumber Standard PS 20 — nominal and actual dimensions
- Western Wood Products Association — pattern profiles and acclimation guidance
Think a number here is wrong? Tell us — we check every report, correct the page, and date the change. Last checked September 15, 2026.