Shiplap Calculator – How Many Boards Do I Need? | CalcLoft
Find out exactly how many shiplap boards you need for a wall, ceiling or accent panel — in square feet, with waste included.
How to calculate shiplap boards for a wall
To estimate shiplap for one wall, multiply the wall length by the wall height to get the area you need to cover:
Wall area = wall length × wall height
Each board covers its width in inches converted to feet, times its length in feet:
Board coverage = (board width in inches ÷ 12) × board length
For example, a 5.5 in wide board that is 12 ft long covers (5.5 ÷ 12) × 12 = 5.5 sq ft. A 12 × 8 ft wall is 96 sq ft, so 96 ÷ 5.5 = 17.5, rounded up to 18 boards before waste. Add 10% for cuts and offcuts and you get 20 boards. The calculator does exactly this.
Shiplap board coverage reference
How many 5.5 in × 12 ft boards (5.5 sq ft each) you need for common wall sizes, with and without the recommended 10% waste:
| Wall size | Wall area | Boards needed | With 10% waste |
|---|---|---|---|
| 8 × 8 ft | 64 sq ft | 12 | 13 |
| 10 × 8 ft | 80 sq ft | 15 | 16 |
| 12 × 8 ft | 96 sq ft | 18 | 20 |
| 12 × 10 ft | 120 sq ft | 22 | 24 |
| 16 × 8 ft | 128 sq ft | 24 | 26 |
Wider boards cover more per piece. A 7.25 in × 12 ft board covers 7.25 sq ft, and a 9.25 in × 12 ft board covers 9.25 sq ft — so a 96 sq ft wall takes about 14 or 11 boards instead of 18.
Horizontal vs vertical shiplap
This calculator estimates the square footage you need, which works the same either way. The classic look is horizontal runs, where each row is one board or more laid end to end across the wall length. A common rows-based check is: rows = wall height (in inches) ÷ board width (in inches), rounded up, times the boards per row = wall length ÷ board length, rounded up. For an 8 ft wall with 5.5 in boards that is 18 rows, and a 12 ft wall with 12 ft boards needs one board per row — so both methods agree at 18 boards. When your wall run is shorter or longer than the board length, offcuts grow and the area method above is the safer estimate. For a vertical accent wall, boards run floor to ceiling: use the wall height as the run and the wall length to count the rows. Either way, keep at least 10% waste in your order.
Related guides
Shiplap calculator FAQ
Shiplap: horizontal or vertical?
Both look great, but horizontal is the classic farmhouse look and the easiest to install. Vertical boards make a ceiling feel taller and are popular on accent walls. This calculator works for either — just enter the wall length and height, and use the wall height as the run if you install the boards vertically.
What does a 1×6 board actually cover?
A nominal 1×6 shiplap board measures about 5.5 in across the face, so that is the coverage width we use — a 12 ft board covers 5.5 sq ft. A 1×8 covers about 7.25 in and a 1×10 about 9.25 in. Measure your own boards if the face width differs, since some brands list a slightly smaller "actual coverage" once the tongue and groove overlap.
Should I really add 10% waste?
Yes — keep the default at 10%. You will cut ends to fit corners, trim around outlets and windows, and lose a board now and then to a knot or a split tongue. Buy more than 10% for diagonal patterns or walls with doors and windows that interrupt the runs.
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