Shiplap Calculator - MyBuildMath

Planning a shiplap wall? Enter the wall size and the board cover width. You get the number of boards, in horizontal rows or vertical.

Wall width (ft)Wall height (ft)Windows and doors (total area) (sq ft)Enter 0 if the wall has none.Board directionBoard cover width (in)A 1×6 shiplap covers about 5 1/8 in. A 1×8 covers about 6 7/8 in. Check the package.Length of boards you buyExtra for mistakes and cuts (%)10% is a safe cushion for most jobs.

Your shopping list

37Boards to buy

19Rows up the wall

112 sq ftWall area to cover

Board length in totalIncludes extra292.6 ft
Area with extra123.2 sq ft
Board length of eachWall width14 ft

Openings are taken out in proportion, so this is an estimate. Pieces include 10% extra. Trim, nails and paint are not counted.

How to use the Shiplap Calculator

Measure the wall width and height. Add the area of windows and doors.
Pick horizontal or vertical boards.
Enter the cover width from the package and pick the board length.
Read your list. Leave the extra at 10%, or 15% for a wall with many cuts.

The math behind it

Rows = wall height (in) / cover width, rounded up

Boards across = wall width (in) / cover width, rounded up

Stock boards = estimate how many stock lengths cover the rows or columns, including waste, then adjust for openings and round up

A worked example

What we typed in

Wall width: 16 ft
Wall height: 9 ft
Windows and doors (total area): 30 sq ft
Board direction: Vertical boards
Board cover width: 5.13 in
Length of boards you buy: 8 ft
Extra for mistakes and cuts: 10%

What we got

Boards to buy: 38
Boards across the wall: 38
Wall area to cover: 114 sq ft
Board length in total: 297.83 ft
Area with extra: 125.4 sq ft
Board length of each: 9 ft

For a related part of your project, use the Rigid Foam Board Insulation Calculator.

Tips from the job site

Start at the bottom for horizontal boards, and check the first row with a level.
Use a spacer for the same gap on every board.
Let the boards sit in the room for 48 hours before you install them.

Common questions

What is the cover width of shiplap?

It is smaller than the board width because of the overlap. Check the package for the exact number.

How much extra shiplap should I buy?

10% for a simple wall and 15% when you have many openings or angles.

Do I take out windows and doors?

Yes. Enter their total area and the tool reduces the count in proportion.

See all Wall Calculators.

How to read the shiplap estimate

In the vertical example, 16 × 9 = 144 square feet before openings. Subtracting 30 square feet leaves 114 square feet, or 125.4 square feet with 10% extra. The calculator estimates 38 stock boards. The 9 ft shown under “Board length of each” is the wall height, so 8 ft stock requires joints. Plan those cuts and joints before ordering.

Last checked: November 15, 2026 (worked example and form display).