Shiplap boards overlap, so each board covers less than its full width. Enter the wall size and the exposed face width; the calculator gives the linear feet and the number of boards to buy.
Shiplap formula
Wall area = width × height − openings Linear feet = area × 12 ÷ exposed width (in) × (1 + waste %) Boards = linear feet ÷ board length, rounded up
Worked example: a 12 × 8 ft wall, 5¼ in exposure
- Area: 96 sq ft.
- Linear feet: 96 × 12 ÷ 5.25 × 1.10 = 241.4 ft.
- In 8 ft boards: 31.
Why exposure matters
A nominal 1 × 6 shiplap board is about 5½ in wide, but the rabbeted overlap hides part of it, so the face you see is narrower. The exact exposure varies by product and is the number that matters; measure a board or check the product sheet. Using the full board width instead underestimates how much you need.
Linear feet per 100 sq ft
| Exposed width | Linear ft (10% waste) |
|---|---|
| 3.5 in | 377 |
| 5.25 in | 251 |
| 7.25 in | 182 |
| 9.25 in | 143 |
Questions
How much shiplap for a 10 × 8 wall?
About 201 linear ft with a 5¼ in exposure and 10% waste.
Do I subtract windows?
Subtract large openings; small ones can stay in as extra.
Can I use this for a ceiling?
Yes; enter the ceiling length and width.
Sources
- NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically, National Institute of Standards and Technology.
Used for: Foot and inch definitions.