Shiplap Calculator
How many shiplap boards cover a wall or ceiling, from its area, the exposed face of each board and the board length.
Result
Enter wall or ceiling areas to see the result.
https://calcgallery.com/lumber-carpentry/shiplap-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use the Shiplap Calculator
- Add one row for each wall or ceiling section, with its length and height.
- Take off the area of windows and doors that will not be covered.
- Enter the exposed face width of your shiplap and the length the boards are sold in.
- Read the boards to buy and the linear length they add up to.
How it is calculated
area to cover = sum of wall rows − openingslinear length = area to cover ÷ exposed face × (1 + allowance)boards = ⌈linear length ÷ board length⌉Dividing an area by the width each board shows gives the total length of board it takes, the same way a lawn divided by the width of a mower gives the distance walked.
Layout tips
Start the first course level, not tight to a floor or ceiling that may not be, and check it every few courses. Plan the courses so that a narrow rip does not end up at the top of the wall where it will be seen; dividing the height by the face width shows how the last course will fall. Stagger the end joints between courses so they do not line up. Behind shiplap, blocking or sheathing may be needed where boards do not land on studs, and fire and moisture rules for wall linings vary by location and must be checked.
With your numbers
- Area to cover = 96 ft² − 0 ft² = 96 ft²
- Linear length = area ÷ 5.5 in × (1 + 0%) = 209.5 ft
- Boards = ⌈209.5 ft ÷ 8 ft⌉ = 27
Quick reference
No extra is added by default. Offcuts are assumed to be used in later courses.
| Job | Boards to buy |
|---|---|
| 12 × 8 ft wall | 27 |
| 10 × 8 ft wall, 6 in face | 20 |
| Two walls, 7 1/4 in face | 17 |
| 12 × 12 ft ceiling | 40 |
| 3.6 × 2.4 m wall | 26 |
| 4 × 2.4 m wall with a door | 24 |
Common questions about the Shiplap Calculator
- How many shiplap boards do I need for a 12 by 8 foot wall?
- The wall is 96 square feet. With a 5 1/2 inch exposed face, each linear foot of board covers 5.5 ÷ 12 of a square foot, so the wall takes about 209.5 linear feet, which is 27 boards of 8 feet.
- What is the exposed face width?
- The part of each board you can see once it is installed. Shiplap has a rabbet along each edge that laps under the next board, so it covers less than its full width. Use the coverage or face width the supplier gives for the exact product, or measure a board and take off the lap.
- Does this work for a ceiling?
- Yes. Enter the ceiling as one more row, length by width. The arithmetic is the same because only the area and the face width matter.
- Why might I need more boards than this?
- The count assumes offcuts from one course start the next. On walls broken up by windows, or where you want no short pieces, more ends up as scrap. Choose Custom and add an allowance for that.