Shiplap Calculator
How much shiplap do I need? Enter your wall dimensions, subtract windows and doors, pick a board size and pattern — get exact board count, lineal feet, waste allowance, trim, and cost.
Calculate your shiplap
100% free · runs entirely in your browser · nothing is uploaded.
1 · Walls
2 · Openings (windows & doors)
3 · Boards & pattern
4 · Cost (optional)
Your shiplap takeoff
What is shiplap?
Shiplap is interior wall paneling made from boards with a rabbet joint — an L-shaped notch milled on opposite edges — so each board overlaps its neighbor and leaves a narrow shadow line. It became the signature look of modern farmhouse interiors: bright painted pine (or MDF) boards running horizontally across an accent wall, fireplace surround, bedroom headboard wall, or ceiling.
What shiplap is not: it is not structural siding, and modern “nickel-gap” looks often use plain square-edge boards spaced a nickel’s width apart to imitate the shadow line. The coverage math is identical — only the exposed face width per board matters.
How this shiplap calculator works
- Wall area. Each rectangle contributes length × height; optional gable triangles contribute ½ × base × rise.
- Subtract openings. Every window and door is deducted at full size — no hidden fudge factors.
- Lineal feet. Net square feet ÷ exposed board width (in feet). A 1×6 exposes 5 in, i.e. 5÷12 ft.
- Boards. Lineal feet ÷ board length, rounded up to whole boards.
- Waste. Boards are multiplied by 1.10 (10%) or 1.15 (15%) and rounded up again — waste covers end joints, miscuts, and damaged boards.
- Trim & extras. Trim lineal depends on pattern; boxes and cost are computed only if you enter those prices.
Shiplap board sizes & real coverage
Lumber is sold by nominal size but milled smaller (actual). The rabbet overlaps about ½ in, so the exposed face — the number this calculator uses — is actual minus ½ in.
| Nominal | Actual width | Exposed face | Covers per 8-ft board | Covers per 12-ft board |
|---|---|---|---|---|
| 1×4 | 3-1/2 in | 3.0 in | 2.0 sq ft | 3.0 sq ft |
| 1×6 | 5-1/2 in | 5.0 in | 3.3 sq ft | 5.0 sq ft |
| 1×8 | 7-1/4 in | 6.75 in | 4.5 sq ft | 6.8 sq ft |
| 1×10 | 9-1/4 in | 8.75 in | 5.8 sq ft | 8.8 sq ft |
| 1×12 | 11-1/4 in | 10.75 in | 7.2 sq ft | 10.8 sq ft |
Horizontal, vertical, or ceiling?
| Pattern | Best for | Trim takeoff | Watch out |
|---|---|---|---|
| Horizontal | Classic farmhouse; makes rooms feel wider; accent walls, fireplace surrounds | Top + bottom runs (2 × wall length) | Start perfectly level — every course magnifies a crooked starter |
| Vertical | Makes ceilings feel taller; entryways, bathrooms, narrow walls | Left + right runs (2 × wall height) | Boards must be ≥ wall height; 8-ft boards suit 8-ft ceilings exactly |
| Ceiling | Bedrooms, porches, kitchens that need character | Full perimeter 2 × (length + width) | Fasten into joists + adhesive; use 12–16 ft boards to cut joints overhead |
Material quantity is the same for all three patterns — only the trim math and handling change.
Worked example: real accent wall
Wall area: 12×9 = 108.0 sq ft; window: 3×4 = 12.0 sq ft; net: 96.0 sq ft.
Lineal feet: 96 ÷ (5÷12) = 230.4 ft.
Boards: 230.4 ÷ 8 = 28.8 → ×1.10 = 31.68 → buy 32 boards (order area 105.6 sq ft).
Courses: 22 horizontal rows; trim: 24.0 lineal ft top + bottom; boxes (15 sq ft/box): 8.
Cost: 32 × $12.49 = $399.68 material; 105.6 sq ft × $4.50 = $475.20 labor; total $874.88.
Quick reference: boards per wall (10% waste included)
No openings. Boards are rounded up — match your wall size and board choice.
| Project | Board | Board length | Net sq ft | Lineal ft | Boards to buy |
|---|---|---|---|---|---|
| 8×8 ft wall | 1×6 | 8 ft | 64.0 | 153.6 | 22 |
| 10×8 ft wall | 1×6 | 8 ft | 80.0 | 192.0 | 27 |
| 12×8 ft wall | 1×6 | 8 ft | 96.0 | 230.4 | 32 |
| 12×9 ft wall | 1×6 | 8 ft | 108.0 | 259.2 | 36 |
| 14×8 ft wall | 1×6 | 8 ft | 112.0 | 268.8 | 37 |
| 16×10 ft wall | 1×6 | 8 ft | 160.0 | 384.0 | 53 |
| 12×12 ft room, 4 walls | 1×6 | 8 ft | 384.0 | 921.6 | 127 |
| 8×8 ft wall | 1×8 | 12 ft | 64.0 | 113.8 | 11 |
| 12×8 ft wall | 1×8 | 12 ft | 96.0 | 170.7 | 16 |
| 14×8 ft wall | 1×8 | 12 ft | 112.0 | 199.1 | 19 |
| 12×12 ft room, 4 walls | 1×8 | 12 ft | 384.0 | 682.7 | 63 |
Pro tips before you buy
- Stagger butt joints by at least 16 in (one stud bay) between courses — never stack joints vertically.
- Nail into studs, two brads per stud per board; mark stud locations on the wall before you start.
- Acclimate boards in the room 48–72 hours so expansion gaps stay honest after install.
- Buy longest boards you can transport: fewer joints, less waste, cleaner look.
- Paint before install (or buy pre-primed) — the rabbet shadow line shows raw wood if you paint after.
- Caulk the perimeter, not the shadow lines: shiplap needs to move seasonally.
Frequently asked questions
How much shiplap do I need for my wall?
Measure each wall's length times height in feet, subtract windows and doors, then divide the net square footage by the board's exposed face width in feet. That gives lineal feet; divide by board length and round up, then add 10% waste (15% for walls with many cuts). Example: a 12x9 ft wall (108 sq ft) minus a 3x4 ft window (12 sq ft) = 96 sq ft net. With 1x6 shiplap (5 in exposed = 0.4167 ft), you need 96 / 0.4167 = 230.4 lineal feet, which is 28.8 eight-foot boards, rounded up to 32 boards with 10% waste.
How do you calculate shiplap?
The standard shiplap formula has five steps: 1) Gross wall area = sum of (length x height) for every wall, plus any gable triangles (0.5 x base x rise). 2) Subtract openings: sum of (width x height) of every door and window. 3) Lineal feet = net area / exposed board width in feet (a 1x6 exposes 5 in, so divide by 5/12). 4) Boards = lineal feet / board length, rounded up. 5) Add waste: multiply by 1.10 (10%) or 1.15 (15%) and round up again. This calculator does all five steps, including trim and cost.
What is the standard waste factor for shiplap?
Order 10% extra shiplap for straightforward walls with few openings, and 15% when the wall has many windows or doors, short wall sections, angled cuts (gables, stair walls), or you are using short offcut-prone board lengths. Waste covers end joints, miscuts, and damaged boards. Never order exact net coverage: one miscut on the last board means a second trip to the store. For ceilings, 10% is usually enough because runs are long and uninterrupted.
What size shiplap boards should I use: 1x6 or 1x8?
1x6 is the most popular shiplap size: its 5-1/2 in actual width exposes 5 in of face per board, giving the classic farmhouse look with more shadow lines per wall. 1x8 (7-1/4 in actual, 6-3/4 in exposed) covers about 35% more area per board, so you buy fewer boards and install faster, with a bolder, more modern look. Use 1x6 for standard 8-ft ceilings and cozy rooms; use 1x8 or wider for tall walls, large rooms, and ceilings where fewer seams look cleaner.
How much wall does one shiplap board actually cover?
A shiplap board covers its exposed face width times its length. The rabbet (shiplap joint) overlaps about 1/2 in, so subtract that from the actual width: a 1x6 (5-1/2 in actual) covers 5 in of wall, a 1x8 (7-1/4 in actual) covers 6-3/4 in, a 1x4 (3-1/2 in actual) covers 3 in, a 1x10 (9-1/4 in actual) covers 8-3/4 in, and a 1x12 (11-1/4 in actual) covers 10-3/4 in. One 8-ft 1x6 board therefore covers 5/12 x 8 = 3.33 sq ft; one 8-ft 1x8 covers 4.5 sq ft.
Should shiplap run horizontal or vertical?
Horizontal shiplap is the classic look and makes a room feel wider; start at the bottom with a level starter course and work up. Vertical shiplap makes ceilings feel taller and suits entryways, bathrooms, and narrow accent walls. The material math is identical either way: net wall area divided by exposed board width. What changes is the trim takeoff (horizontal needs top and bottom trim runs; vertical needs side trim runs) and handling: vertical boards must be at least as long as the wall is tall, so 8-ft boards suit 8-ft ceilings exactly.
Do I subtract windows and doors from shiplap calculations?
Yes. Subtract the full area of every door and window from the gross wall area before calculating boards. Pros subtract every opening; DIY rules of thumb that skip openings under a few square feet exist to build in hidden waste, but they over-order on walls with big openings and make the math impossible to verify. This calculator subtracts exactly what you enter, then adds an explicit 10-15% waste factor, so nothing is hidden.
How many nails do I need per shiplap board?
Fasten each shiplap board to every wall stud it crosses, typically with two 15- or 16-gauge brads (or one 2 to 2-1/2 in finish nail) per stud. Studs are usually 16 in on center, so an 8-ft board crosses about 6 studs and needs roughly 12 nails; a 12-ft board needs about 18. Use 2-in brads for 3/4-in shiplap over drywall. For a whole wall, estimate nails as boards x (board length in inches / 16, rounded up) x 2.
Can I install shiplap on the ceiling?
Yes, shiplap ceilings are a popular way to add character, and the calculation is the same: ceiling area (length x width) divided by exposed board width gives lineal feet. Use the ceiling pattern in this calculator: it runs boards across the shorter dimension by default and computes trim as the ceiling perimeter. Use 12-ft or 16-ft boards to minimize joints overhead, add 10% waste, and always fasten into joists (24 in on center typical) with construction adhesive plus nails for safety.
How much does it cost to shiplap a wall?
Material cost depends on board size and species: primed pine or MDF 1x6x8 ft boards typically run $8-$16 each, so a 12x8 ft accent wall needing about 32 boards costs roughly $260-$510 in boards plus trim, caulk, and paint. Professional installation usually adds $3-$7 per square foot. Enter your per-board price and local labor rate in this calculator for an exact material and labor estimate with waste included.
What board length should I buy: 8, 12, or 16 ft?
Buy the longest boards your wall (and vehicle) can handle. Longer boards mean fewer butt joints, less visible seaming, and less cut waste: a 14-ft wall needs two 8-ft boards per course with a joint and offcut, but a single 16-ft board with one clean cut. Use 8-ft boards for walls up to 8 ft long or 8-ft ceilings with vertical shiplap; 12-ft boards for 10-12 ft walls; 16-ft boards for long walls and ceilings. Always stagger butt joints by at least 16 in (one stud bay) between courses.
What is the difference between shiplap, tongue-and-groove, and nickel-gap?
True shiplap has a rabbet (L-shaped notch) on opposite edges so boards overlap, creating a small shadow line. Tongue-and-groove boards interlock with a hidden joint for a tight, nearly seamless surface. Nickel-gap is a modern install style: square-edge boards spaced a nickel's width apart (about 1/16-1/8 in) to mimic shiplap's shadow line. The coverage math is the same for all three: net area divided by exposed face width. Only the look, price, and moisture behavior differ.
Related calculators
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- Drywall Calculator — sheets, screws & mud for the walls behind
- Wallpaper Calculator — rolls for the walls you are not shiplapping
- Vinyl Siding Calculator — exterior counterpart: squares, panels & trim
Free tool by NRTechStudio