Shiplap Calculator
Use this shiplap calculator to estimate how many shiplap boards you need for walls, ceilings, or exterior siding. Shiplap is a popular cladding style where boards overlap with a rabbet joint, creating a tight, weather-resistant surface. This calculator helps you figure out board count, total linear feet, waste allowance, and rough material cost so you can plan your purchase more confidently. Whether you are finishing an accent wall in a living room, cladding a bedroom ceiling, or installing exterior siding on a shed, the tool adapts to your dimensions and board size.
Popular searches:
Width of the wall to be covered.
Height of the wall to be covered.
Face width of each shiplap board.
Length of each shiplap board.
Overlap between boards.
Extra for cuts and defects.
Optional cost estimate.
Doors/windows to subtract.
Result
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Boards needed
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Linear feet
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Rows
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Total cost
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Quick Answer:
To estimate shiplap boards, divide the wall width in inches by the net exposed face width of one board (board width minus overlap). That gives the number of boards per row. Multiply by the wall height to get total linear feet. Example: a 12 ft wide wall using 6 inch boards with 0.5 inch overlap needs about 26 boards per row. At 8 ft tall, that is roughly 208 linear feet before waste.
How to Calculate Shiplap Coverage
- Measure the surface: Enter the wall width and wall height in feet. For ceilings, use width and length. Subtract any large openings like doors or windows if you want a closer estimate.
- Enter board dimensions: Provide the face width of the shiplap board in inches and the board length in feet. Common shiplap boards are 6 inches wide and 8 feet long, but sizes vary by manufacturer.
- Set the overlap: Shiplap boards overlap at the rabbet joint. Enter the overlap amount in inches. A typical overlap is 0.5 inches, but check your specific product.
- Add waste and price: Include a waste allowance for cuts, defects, and fitting around openings. A 10% allowance is common. If you know the price per linear foot, enter it to estimate total material cost.
Shiplap Calculator Formula
Boards per row = (wall width x 12) / (board width - overlap) | Total linear feet = boards per row x wall height | Linear feet with waste = total linear feet x (1 + waste%)
| Variable | Meaning | Unit |
|---|---|---|
| Wall width | Width of the wall or ceiling to be covered | ft |
| Wall height | Height of the wall or length of the ceiling | ft |
| Board width | Nominal face width of one shiplap board | in |
| Overlap | Amount each board overlaps the adjacent board | in |
| Waste | Extra percentage for cuts, defects, and fitting | % |
Worked Examples
USA - Accent wall in a living room
- Wall width: 12 ft
- Wall height: 8 ft
- Board width: 6 in
- Board length: 8 ft
- Overlap: 0.5 in
- Waste: 10%
Result: About 26 boards and 208 linear feet before waste, roughly 229 linear feet with waste
This is a typical accent wall project. The calculator estimates board count and linear feet so you can compare supplier pricing and plan your installation sequence.
UK - Bedroom ceiling cladding
- Wall width: 10 ft
- Wall height: 12 ft
- Board width: 150 mm
- Board length: 2.4 m
- Overlap: 12 mm
- Waste: 8%
Result: About 24 boards and 288 linear feet before waste, roughly 311 linear feet with waste
Ceiling projects often need longer boards and careful layout planning. The waste factor helps account for cuts around light fixtures and edges.
EU - Exterior shed siding
- Wall width: 8 ft
- Wall height: 7 ft
- Board width: 6 in
- Board length: 10 ft
- Overlap: 0.5 in
- Waste: 12%
Result: About 18 boards and 126 linear feet before waste, roughly 141 linear feet with waste
Exterior siding needs a higher waste allowance because boards must be cut to fit around corners, windows, and weatherproofing details.
GCC - Feature wall in a modern apartment
- Wall width: 4 m
- Wall height: 2.7 m
- Board width: 150 mm
- Board length: 2.7 m
- Overlap: 10 mm
- Waste: 10%
Result: About 34 boards and 92 linear meters before waste, roughly 101 linear meters with waste
Metric calculations work the same way. Convert all measurements to consistent units before calculating, then convert back if needed for ordering.
Shiplap Coverage Chart
| Range | Meaning | Planning action |
|---|---|---|
| Under 100 linear ft | Small accent wall or short section | A few bundles may be enough. Check bundle size and board length before buying. |
| 100 to 300 linear ft | Typical room accent wall or small ceiling | Compare pricing per board versus per linear foot. Waste allowance matters more at this scale. |
| 300 to 600 linear ft | Multiple walls or a full room | Plan the layout carefully to minimize cuts. Consider ordering an extra bundle for defects and future repairs. |
| Over 600 linear ft | Whole-house siding or large commercial feature | Coordinate delivery, staging, and installation sequence. Verify board lot consistency to avoid color or texture variation. |
Frequently Asked Questions
Shiplap is a type of wooden board with a rabbet joint cut along the edges. When installed, each board overlaps the adjacent one, creating a tight, weather-resistant surface. It is popular for interior accent walls, ceilings, and exterior siding on sheds, cabins, and modern homes.
Measure the wall width in inches and divide by the net face width of one board (board width minus overlap). That gives the number of boards per row. Multiply by the wall height in feet to get total linear feet. Add a waste allowance for cuts and defects.
A common overlap is 0.5 inches (about 12 mm), but it depends on the board profile and manufacturer. Some shiplap products have a deeper rabbet that requires more overlap. Always check the product specifications before calculating.
Yes. Shiplap is a popular choice for ceilings, especially in bedrooms, living rooms, and porches. The calculation method is the same: measure the ceiling area, divide by the net face width, and multiply by the ceiling length to get total linear feet.
A 10% waste allowance is common for interior walls. For exterior siding or complex layouts with many openings, consider 12% to 15%. Waste covers cuts, defects, fitting around outlets, and the small pieces that cannot be used.
Shiplap boards overlap at the rabbet joint, leaving a small shadow line between boards. Tongue-and-groove boards interlock with a tongue on one edge and a groove on the other, creating a tighter, more seamless joint. Shiplap is easier to install and more forgiving of slight variations.
Yes. Shiplap can be installed directly over drywall using construction adhesive and finish nails. Make sure the drywall is in good condition and the wall is flat. Some installers add a thin plywood backer for extra holding strength.
Multiply the total linear feet (including waste) by the price per linear foot. Some suppliers price shiplap by the board, so multiply the board count by the price per board. Always confirm pricing with your supplier before ordering.
This calculator is built to give a fast planning estimate, not a final field measurement. Enter the project dimensions, keep the units consistent, and treat the result as a starting point for ordering or budgeting. For Shiplap, it is smart to round up when cuts, fit-up, or supplier packaging could increase the real purchase amount.
The quickest way to use the page is to match your real project measurements to the inputs, then let the formula do the unit conversion for you. If you are estimating Shiplap, check whether the result is meant to be rounded up, especially when the material is sold in standard lengths, panels, bags, or batches.
Most of the accuracy comes from good measurements. If the width, length, depth, or density is off, the result will move with it. For Shiplap, that means measuring the work area carefully and confirming product specs before you place an order.
Yes, metric inputs are usually fine as long as you keep the same unit system throughout the calculation. The key is consistency: do not mix feet with metres or inches with millimetres unless the calculator specifically converts between them. That rule is especially important for Shiplap.
A planning calculator cannot know every site detail, so a small waste allowance is often wise. For Shiplap, waste covers trimming, damage, overlaps, layout changes, or the bits left over after cutting. If your project is complex, use a slightly higher margin.
Rounding depends on what you are buying. If the answer is a count, round up to the next whole item. If it is an area or volume, compare the output to the way your supplier sells materials. For Shiplap, a conservative round-up usually saves time later.
Openings, cutouts, and unusual shapes can change the total a lot. When the calculator offers a way to subtract them, enter them carefully so you do not overbuy. For Shiplap, large holes or interruptions are often worth deducting before adding your waste allowance.
The calculator is useful for comparing materials because it keeps the project math in one place. You can swap in different widths, densities, exposures, or lengths to see how the order changes. That makes Shiplap a practical tool for side-by-side planning.
The result is accurate enough for estimating, pricing, and comparing options, but it should not replace manufacturer instructions or engineering review when the project is structural. For Shiplap, use the output as a planning figure and verify code or product limits separately when needed.
Small measurement changes can have a noticeable effect, especially on large projects. If your numbers are approximate, run a second pass with the next likely size up or down. For Shiplap, that quick sensitivity check helps avoid short orders.
Yes. Many people use the result to estimate cost by multiplying the quantity or area by a unit price from a supplier. For Shiplap, that is often the easiest way to compare quotes before you decide what to buy.
Contractors and DIY users can both benefit from the same calculation because the underlying math is the same. What changes is the level of precision and the amount of waste you choose to carry. For Shiplap, a contractor may use a tighter estimate while a DIYer may prefer a little extra margin.
Planning note: This calculator provides planning estimates only. Actual board count and linear feet can vary with board profile, installation method, opening sizes, waste handling, and site conditions. For large projects or exterior siding, verify dimensions and product specifications with your supplier before ordering.
References
- Omni Calculator - Shiplap Calculator
- This Old House - Shiplap Siding Guide
- Family Handyman - How to Install Shiplap
Last reviewed: March 2026