Shiplap Calculator: Boards, Area, and Cost Estimator
Enter your wall dimensions, board size, and optional door or window areas to find out exactly how many shiplap boards you need. The calculator adds your chosen waste factor, shows a per-board and total cost estimate, and breaks the math down step by step so you can sanity-check every number before you buy.
What is shiplap and how is coverage calculated?
Shiplap is a wood cladding style where each board has a rabbet (notch) cut along its top and bottom edge so successive boards overlap slightly, creating a tight, weather-resistant joint with a small reveal between each row. The reveal - the visible face of each board - is always slightly narrower than the board's actual width, so every installation formula must use the effective coverage width rather than the nominal or actual dimension. For a 1x6 board (5.5 inches actual), the exposed face is typically about 5.3 inches with a standard 3/16-inch gap. Multiply that by the board's length to get the square footage each board covers: 5.3/12 ft x 8 ft = 3.53 ft². Dividing the net wall area by this number gives the base board count, and adding a waste percentage accounts for off-cuts, broken boards, and mistakes.
How to choose the right board size and length
The most popular residential choice is 1x6 shiplap: wide enough to show grain character without making a small room feel heavy, yet manageable to handle alone. Narrower 1x4 boards suit bathrooms, accent walls, and spaces where you want a busier, more textured look. Wider 1x10 or 1x12 boards are common on exterior siding and open-plan great rooms where they provide a more contemporary, airy feel. Board length should ideally match or exceed your wall width so you avoid vertical seams, but in practice 8-foot boards work for most residential walls. If your wall is wider than the board, stagger the seams at least 16 inches apart and land them on a stud. For ceilings, a 12-foot or 16-foot board dramatically reduces the number of seams across the span.
Waste factor: how much extra should you buy?
A 10% waste factor is the standard recommendation for a straightforward horizontal installation on a plain wall: you will make a cut at the end of every row, and some cuts on short walls produce a piece too small to reuse. Bump the allowance to 15% if the wall has multiple windows and doors, since you will cut around each corner and the off-cuts are less likely to fit elsewhere. Choose 20% for diagonal or herringbone patterns, which create far more angle cuts and awkward triangular waste pieces. Shiplap from solid pine or cedar comes in consistent lengths but can include boards with knots or splits you will want to reject, so a small buffer is wise even on the simplest project. Always verify the return policy at your supplier before ordering; some retailers will take back full, unopened bundles.
Material costs and budget planning
Solid wood shiplap ranges from about $1.50 to $7 per square foot of material, depending on species and grade. Common pine is the least expensive and easiest to paint. Knotty pine gives a rustic character for slightly more. Cedar resists moisture naturally, making it the go-to for bathrooms and mudrooms despite a higher price. White oak and other hardwoods can reach $10-$15 per square foot for a premium look. MDF and engineered shiplap (around $1-$2/ft²) are budget options that take paint well but are vulnerable to moisture. Professional installation typically adds $1.50 to $3.50 per square foot on top of materials: a 120 ft² accent wall might cost $500-$1,000 all in, while a full room could easily run $2,000-$4,000 installed.
Shiplap board sizes: actual dimensions and coverage
| Nominal size | Actual width | Coverage / 8 ft board | Boards per 100 ft² |
|---|---|---|---|
| 1x4 | 3.5" | 2.33 ft² | 43 |
| 1x6 | 5.5" | 3.67 ft² | 28 |
| 1x8 | 7.25" | 4.83 ft² | 21 |
| 1x10 | 9.25" | 6.17 ft² | 17 |
| 1x12 | 11.25" | 7.50 ft² | 14 |
Coverage per 8-foot board with no gap (traditional shiplap). Add a 3/16-inch gap for nickel-gap or standard gap style.
Frequently asked questions
How many boards do I need for a 12x9 foot wall?
A 12 x 9 ft wall has 108 ft² of gross area. With 1x6 shiplap (8-foot boards covering about 3.53 ft² each), you need about 31 boards as a base count. Add 10% waste and you should buy 35 boards. Use this calculator with width 12, height 9, and 1x6 board size for the exact figure adjusted for any windows or doors.
What is the difference between shiplap and nickel-gap shiplap?
Traditional shiplap overlaps slightly, with no visible gap between rows - the rabbet joint tucks behind the board above. Nickel-gap shiplap leaves a small, uniform space (about 1/8 inch, the thickness of a nickel) between each row for a more contemporary look. Nickel-gap uses slightly more boards per square foot because each exposed face is a little narrower. This calculator lets you choose no gap, 1/8-inch (nickel gap), 3/16-inch (standard), or 1/4-inch gap to reflect your style.
Should I install shiplap horizontally or vertically?
Horizontal installation is the classic farmhouse look - boards run parallel to the floor and create a sense of width. Vertical installation (also called board-and-batten style when using shiplap) adds height and is popular in coastal and cottage interiors. Diagonal or herringbone patterns are decorative accent choices but produce more waste (budget 15-20%) and require more precise cuts. This calculator works for any orientation: just swap width and height if you want vertical runs, or increase the waste factor for diagonal patterns.
How do I account for windows and doors?
Measure the width and height of each window or door opening, multiply to get its area, and add them all together. Enter that total in the "Total opening area" field. The calculator subtracts it from the gross wall area before computing board count. Note that the boards still need to be cut around openings - you will not save full boards, only portions - which is one reason the waste factor matters more on walls with many openings.
What tools do I need to install shiplap?
A miter saw (for clean crosscuts to length), a table saw or circular saw with a guide (for ripping the first and last rows to width), a nail gun with 2-inch finish nails, a level, and a stud finder are the core tools. A spacer cut from scrap wood or a handful of nickels helps maintain a uniform gap on nickel-gap installs. Prime or seal the backs of the boards before installation to prevent moisture from warping the face side.
Do I need to acclimate shiplap before installation?
Yes, especially for solid wood. Stack the boards flat in the room where they will be installed for at least 48-72 hours (some manufacturers recommend up to a week) so the wood adjusts to the ambient temperature and humidity. Skipping this step can cause boards to expand or contract after installation, creating gaps or buckling. MDF and engineered shiplap are more stable but still benefit from a 24-hour acclimation period.