Shiplap Calculator
Find how much shiplap you need for an accent wall, a whole room, or a ceiling. Enter the walls and ceiling, subtract doors and windows, and choose your nickel gap, shiplap, or tongue and groove boards to see the boards, linear feet, and packs to buy.
Add more walls or a ceiling (its length and width), or subtract doors and windows.
- Choose US or Metric. You can still change the unit of any single field.
- Measure each wall. Run a tape measure along the bottom of the wall for its width, and from the floor to the ceiling for its height. For a single wall, choose Rectangle and enter the width as Length and the floor to ceiling height as Height. For all four walls of a room, choose Room walls and enter the length and width of the room and the wall height.
- For a ceiling, use Add section, keep Rectangle, and enter the length of the room as Length and its width as Height.
- To leave out doors and windows, add a section for each one and set it to Subtract. Use Quantity for several of the same size.
- Choose the Board profile. For another board, choose Custom exposure and enter the exposure from the label.
- Check the Board length, and enter the Boards per pack if the boards come in packs.
- Check the Waste allowance. It starts at 10%.
- Optionally, enter a price per board, per pack, per ft², per m², per ft, or per m to estimate the cost.
Dimension fields accept whole numbers, decimals, fractions, and mixed
numbers, such as 12, 7.5, 3/4, or
4 5/8.
How much shiplap you need
The calculator finds the area of the walls and ceiling, subtracts the openings, adds the waste allowance, and divides by the area that one board covers:
Total area = net area × (1 + waste % ÷ 100)
Boards = total area ÷ (board length × exposure), rounded up
Total board length = total area ÷ exposure
The exposure is the width of the face that shows once the boards are fitted together. Each board laps over or into the next, so the exposure is less than the full width of the board, and using it counts the overlap. The total board length is the boards laid end to end, in linear feet or meters. It depends only on the exposure, so it stays the same whatever length of board you buy. Use it to order from a lumber yard by the linear foot.
With several sections, the calculator adds the sections set to Add and subtracts those set to Subtract. The area of each shape is calculated as follows:
| Shape | Area |
|---|---|
| Rectangle | length × height |
| Room walls | 2 × (length + width) × height |
| Triangle (base and height) | base × height ÷ 2 |
| Known area | the area you enter |
For the gable wall of an attic room, add a Triangle with the width of the wall as the Base and the height from the floor of the slope to the peak as the Height.
The calculator subtracts doors and windows by their area. If you don't subtract the small windows, the extra covers the cuts around them. It counts by area and doesn't lay out each row. Metrie's shiplap guide counts boards the same way, dividing the wall area by the area of one board, and staggers the joints from row to row, so offcuts from the end of one row start the next.
Shiplap board sizes
The count depends only on the exposure and the length of each board. The same nominal size can have a different exposure, so the calculator lists the exposure of each profile:
| Profile | Exposure |
|---|---|
| 1x6 nickel gap | 4 5/8 in |
| 1x8 nickel gap | 6 7/16 in |
| 1x6 rabbeted shiplap | 5 in |
| 1x8 rabbeted shiplap | 6 3/4 in |
| 121 mm softwood shiplap (UK) | 109 mm |
The nickel gap exposures are the exposed face of UFP-Edge's prefinished interior shiplap. The rabbeted shiplap exposures are the face widths for shiplap with a 1/2 in lap in PS 20-20, the American Softwood Lumber Standard. These are minimum dressed sizes, and some lumber is a little wider. The metric exposure is the face cover of Wickes' 12 × 121 mm softwood shiplap cladding, which comes in 2.4 m and 1.8 m lengths.
Other boards have their own exposures. Choose Custom exposure and enter the number on the label:
| Board | Exposure |
|---|---|
| Woodtone 1x6 prefinished shiplap | 4 3/4 in |
| Woodtone 1x8 prefinished shiplap | 6 1/2 in |
| Great American Spaces 1 × 6 in shiplap | About 4.94 in |
| Metrie 5 1/2 in shiplap | 5 in |
| Metrie 7 1/4 in shiplap | 7 in |
| 1x6 shiplap with a 3/8 in lap | 5 1/8 in |
| 1x8 shiplap with a 3/8 in lap | 6 7/8 in |
Labels call the exposure the exposed face, face cover, or coverage. Don't enter the full width of the board, such as 5 1/4 in for a 1x6 nickel gap board, or the count comes out short by the overlap. Whether a nickel gap exposure includes the 1/8 in gap depends on the label. If it doesn't, the count comes out a little high.
Tongue and groove boards count the same way. Enter the face width without the tongue as a Custom exposure. In Australia and New Zealand, the cover of lining boards differs from product to product, so enter the cover from the label as a Custom exposure too.
The same board is often sold in several lengths, such as 8 ft and 16 ft for UFP-Edge, 12 ft for Woodtone, and 12 ft and 16 ft for Great American Spaces. Enter the length you buy as the Board length. Longer boards mean fewer boards and fewer joints.
Shiplap on a ceiling
Shiplap boards are made for walls and ceilings, and a ceiling takes the same boards at the same exposure. Add the ceiling as a Rectangle with the length of the room as Length and its width as Height. For a sloped or vaulted ceiling, measure along the slope from the wall to the peak and use that as the Height of each side.
The waste allowance covers the cuts at the ends of each wall, around doors, windows, and outlets, and along the edges of the ceiling. Great American Spaces and Panel Processing both suggest adding 10%, and Great American Spaces recommends buying the whole job at once so the color matches. For gable walls, sloped ceilings, or rooms with many corners, raise the allowance.
Shiplap siding on the outside of a house
This calculator is for interior boards, like the UFP-Edge shiplap its nickel gap sizes come from, which is made for interior walls and ceilings. For shiplap or other lap siding on exterior walls, including UK PVC shiplap cladding, use the Siding Calculator. For vertical boards with battens, use the Board and Batten Calculator.
Examples
An accent wall
A wall 12 ft wide and 8 ft high is 96 ft², or 105.6 ft² with 10% added. A 1x6 nickel gap board 8 ft long covers 96 × 4 5/8 = 444 in², or 3.08 ft², so 105.6 ÷ 3.08 = 34.3, and you need 35 boards. Laid end to end, that's 273.99 ft of board. In packs of 6, that's 6 packs.
Other profiles and lengths for the same wall
With 1x8 nickel gap you need 25 boards, with 1x6 rabbeted shiplap 32, and with 1x8 rabbeted shiplap 24. With 1x6 nickel gap in 16 ft lengths you need 18 boards, and in 12 ft lengths 23. The total board length stays at 273.99 ft.
A room with a ceiling
A room 12 × 10 ft with 8 ft walls has 2 × (12 + 10) × 8 = 352 ft² of wall. Subtract a door 3 × 7 ft (21 ft²) and two windows 3 × 4 ft (24 ft²), and the net area is 307 ft², or 337.7 ft² with 10% added. That's 110 boards of 1x6 nickel gap 8 ft long. Adding the ceiling, 12 × 10 = 120 ft², brings the total to 469.7 ft² and 153 boards.
Pricing per pack or per linear foot
For the accent wall, if a pack of 6 costs $70, the 6 packs cost $420.00. At $1.25 per linear foot, 273.99 ft costs $342.49.
Metric dimensions
A wall 4 m wide and 2.4 m high is 9.6 m², or 10.56 m² with 10% added. A 121 mm softwood shiplap board 2.4 m long with a 109 mm exposure covers 0.2616 m², so you need 41 boards, 96.88 m of board, or 11 packs of 4. With 1.8 m boards, you need 54.
FAQ
About 35 boards of 1x6 nickel gap 8 ft long, with 10% added for waste. The wall is 96 ft², or 105.6 ft² with waste, and each board covers 3.08 ft². With 16 ft boards, it's 18.
Its length times its exposure. A 1x6 nickel gap board with a 4 5/8 in exposure covers 3.08 ft² at 8 ft long, 4.63 ft² at 12 ft, and 6.17 ft² at 16 ft. A 121 mm softwood shiplap board 2.4 m long covers 0.26 m².
The wall height divided by the exposure, rounded up. An 8 ft wall is 96 in high, so with a 4 5/8 in exposure it takes 96 ÷ 4 5/8 = 20.8, or 21 rows. With a 5 in exposure, it takes 20 rows.
Your total area divided by 32 ft², rounded up. For a 12 × 8 ft wall with 10% added, that's 105.6 ÷ 32 = 3.3, or 4 panels. This calculator counts individual boards, not sheets.
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