Shiplap Calculator
Enter your walls, the board's exposed face and length and get how many shiplap boards to buy, counted row by row and by area, with linear feet and cost.
What shows after the overlap — measure or check the product.
Boards run horizontally. The result updates as you type.
Shiplap boards
42 boards of 8 ft
96 ft² net · 19 courses · 247 linear ft by area
| Rows (courses) per wall | wall 1: 19 |
| Boards counted course by course | 42 (with allowance) |
| Boards by area (offcuts reused) | 31 (with allowance) |
| Wall area | 96 ft² gross, 96 ft² net |
What this page cannot tell you
How joints will be staggered or how offcuts fall. The course count assumes each row starts with fresh boards, which usually overestimates; the area count assumes every offcut is used, which underestimates. Real needs sit between the two. Openings are only subtracted in the area figure.
How to calculate shiplap
- Measure each wall. Width and height in feet.
- Enter the exposed face. What each board shows after the overlap, in inches.
- Enter the board length. 8, 12 or 16 ft — whatever you'll buy.
- Subtract openings and add waste. Window and door area, and an allowance.
- Read the boards. A row-by-row count and an area count, with linear feet.
10 situations where a shiplap calculator helps
Accent wall behind a TV or bed
Exact boards for one wall.
Whole-room shiplap
Add each wall and get one total.
Ceiling planks
Treat the ceiling as a wall: length × width.
Choosing board length
Compare 8 ft and 16 ft boards by count and joints.
Real vs nominal width
Enter the exposed face so the count isn't short.
Bathroom wainscot in shiplap
Set the height to your wainscot height.
Pricing per board
Boards × price for a budget.
Checking a kit
Compare a panel kit's coverage with the boards needed.
Exterior shiplap siding
Courses per wall for a shed or cabin.
Planning joints
Courses per wall show how many rows to lay out.
How the boards are counted
This is arithmetic with no outside data. Boards run horizontally, so each wall needs ceil(height ÷ exposed face) rows (courses), and each course needs ceil(wall width ÷ board length) boards. That course-by-course count assumes every row starts with fresh boards.
The area count is the other bound: net area (walls minus openings) × 12 ÷ exposed face gives linear feet, ÷ board length gives boards, assuming every offcut gets used somewhere. Real jobs land between the two; your waste allowance is applied to both.
Exposed face matters: shiplap boards overlap, so a nominal 1×6 covers less than 5½ in. Measure an installed board or check the product's coverage. Limits: the page doesn't plan stagger, cuts around outlets or where openings fall. Everything runs in your browser.
Frequently asked questions
How many shiplap boards do I need for a wall?
Rows = height ÷ exposed face (rounded up); boards per row = width ÷ board length (rounded up). A 12 × 8 ft wall with 5.125 in exposure and 8 ft boards is 19 rows × 2 = 38 boards.
What width is shiplap?
It varies by product; enter the exposed face after the overlap, not the nominal size.
Why are there two counts?
One assumes no offcuts are reused (more boards), the other that all are (fewer). Real needs sit between.
Should I subtract windows?
The area count subtracts the openings you enter; the row count doesn't, because rows usually run past small openings.
How much extra should I buy?
Your call — the allowance you enter is applied to both counts.
Can I use this for a ceiling?
Yes, enter the ceiling's length and width as one wall.
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