About the Shiplap Calculator
This shiplap calculator works out how much shiplap, nickel-gap or tongue-and-groove paneling you need for an accent wall, a whole room or a ceiling. Enter the wall length and height, subtract any windows or doors, and give the exposed face width and length of the boards you are buying; it returns the linear feet, the number of boards with waste, the number of rows and the material cost.
The number that matters is the exposed face (coverage) width, not the nominal size. A “1 × 6” shiplap board is about 5-1/2 inches wide, but the overlapping rabbet or tongue hides part of it, so each row typically covers around 5 to 5-1/4 inches. Check the coverage width on the product label or measure a board as installed.
Add about 10% for cuts, end joints and defects on a plain wall, and 15% or more for walls with many openings, angled ceilings or a pattern where end joints must be staggered. The same math works for vertical installs: just enter the wall width as the length and the height as the height.
With the default inputs, the boards needed is 31. Change any value above to recalculate instantly.
How to use the shiplap calculator
- 1Measure the wall length and height in feet.
- 2Add up and subtract the area of windows and doors.
- 3Enter the exposed face width of the board, not its nominal size.
- 4Enter the board length you will buy and a waste allowance.
- 5Read the number of boards, rows and the total cost.
Formula and method
Each board covers a strip as wide as its exposed face, so the linear footage needed is the net wall area in square feet × 12 (to work in inches) ÷ the face width in inches. Waste is added for cuts, end joints and rejected boards, and dividing by the board length then rounding up gives the boards to buy.
The number of rows is the wall height in inches divided by the face width, rounded up; the remainder tells you how wide the final ripped row will be. Openings are subtracted by area, which slightly underestimates offcuts around windows, so use a higher waste allowance on walls with several openings.
- L, H
- Wall length and height (ft)
- face
- Exposed coverage width per board (in)
- LF
- Linear feet of board
Worked examples
12 × 8 ft accent wall in 1×6 shiplap
A 96 sq ft wall at 5-1/8 in coverage needs 96 × 12 ÷ 5.125 = 224.8 linear feet, or 247.3 with 10% waste. That is 30.9 boards of 8 ft, so buy 31 — about $372 at $12 each. The wall takes 19 rows.
14 × 9 ft wall with a window, 1×8 boards in 12 ft lengths
The net area is 126 − 15 = 111 sq ft. At 7-1/8 in coverage that is about 187 linear feet, 205.6 with waste, so eighteen 12 ft boards in 16 rows.
12 × 10 ft tongue-and-groove ceiling, 15% waste
Narrow 3-1/4 in T&G needs much more board: 120 sq ft × 12 ÷ 3.25 = 443 linear feet, or 510 with 15% waste. Each 8 ft board covers only 2.17 sq ft, so the ceiling takes 64 boards.
Frequently asked questions
How do I calculate how much shiplap I need?+
Multiply wall length by height to get square feet, subtract openings, multiply by 12 and divide by the board’s exposed face width in inches to get linear feet. Add about 10% waste and divide by the board length to get the number of boards.
How many square feet does a shiplap board cover?+
An 8 ft board with 5-1/8 in of exposed face covers about 3.4 sq ft; a 12 ft board covers about 5.1 sq ft. Narrow 3-1/4 in tongue-and-groove covers only about 2.2 sq ft per 8 ft board.
What is the actual coverage of 1x6 shiplap?+
A nominal 1×6 board is about 5-1/2 in wide, and the overlap typically hides 1/4 to 1/2 in, leaving roughly 5 to 5-1/4 in of coverage. Products differ, so check the coverage or exposure figure listed by the manufacturer.
How much extra shiplap should I buy?+
Buy about 10% extra for a simple rectangular wall and 15–20% for walls with several windows, angled ceilings or staggered end joints. Leftover boards are handy for future repairs.
Can I use this for a vertical shiplap wall?+
Yes. Coverage depends only on area and face width, so the linear footage and board count are the same. For vertical installs, choose a board length at least as long as the wall height to avoid end joints.