Shiplap Calculator

Shiplap is one of the most popular wall treatments for farmhouse and modern-rustic interiors. Getting the board count right before heading to the lumber yard saves money and avoids mid-project supply trips. This shiplap calculator does the math on boards, linear footage, and cost while showing you a visual wall preview.

Understanding Shiplap Board Dimensions

Standard shiplap is sold in nominal widths, but the actual face you see on the wall is smaller. A nominal 1×6 board has a 5.5-inch actual face width. With a 3/8-inch rabbet (overlap), the exposed face per board is approximately 5.125 inches. This means covering a 9-foot (108-inch) wall height with horizontal 1×6 shiplap requires: 108 ÷ 5.125 = 21 boards, not the 18 you might guess from nominal measurements.

Nickel-gap shiplap leaves a deliberate 1/16-inch gap between boards for a modern paneled look. This gap slightly reduces the effective coverage per board — a 5.5-inch board with nickel gap covers about 5.4375 inches, a small difference that becomes relevant on tall walls. The calculator accounts for whichever board width you select.

Step 1: Enter Wall Dimensions

Measure the width and height of your wall or ceiling in feet. For a wall with a window or door, measure the full wall and subtract openings after — most installers buy for the full wall and work around openings using cut-off pieces. Switch to metric if needed using the units toggle.

Step 2: Choose Board Width and Orientation

The most common shiplap profile is 5.5-inch face width (nominal 6-inch), which gives the classic horizontal-plank farmhouse look. Narrower 3.5-inch boards create a more traditional appearance with tighter lines. Nickel-gap (3-inch) leaves a small consistent reveal for a modern twist. Horizontal orientation is standard for walls; vertical can make ceilings feel higher.

Step 3: Calculating Waste Factor

Waste factor accounts for boards cut short at room edges, corners, and openings. Use these guidelines: 10% for simple rectangular walls with no openings; 15% for walls with windows, doors, or inside corners that require more cross-cuts; 20% for diagonal shiplap patterns where every board needs two angled cuts. For a ceiling installation add an extra 5% because boards must be cut on both ends to fit within the joists.

For a 12×9 ft wall (108 sq ft): at 10% waste, order 118.8 sq ft worth of boards — that is 23 standard 12-foot 1×6 boards. At 15% waste for a wall with two windows, order 124.2 sq ft, roughly 25 boards. Buying one or two extra boards is cheap insurance against a bad cut.

Shiplap vs. Tongue-and-Groove

Shiplap uses a rabbet cut on the board edge — a simple step profile that lets boards stack with a slight overlap. Tongue-and-groove boards have a protruding tongue on one edge and a matching groove on the other for a tighter, nearly seamless fit. Tongue-and-groove is preferred for ceilings because boards lock together and resist sagging over long spans. Shiplap installs faster and handles minor width variation better, making it more forgiving on walls where boards may not be perfectly straight.

Both profiles use the same material quantity calculation — the difference is in profile shape, not coverage area. The shiplap calculator works for tongue-and-groove as well; just enter the exposed face width of your specific board profile.

Installation Tips That Affect Material Quantity

Horizontal installation (the classic look) runs boards parallel to the floor. Start at the bottom and work up, which means the cut boards end up at the top where they are less visible. Vertical installation runs boards perpendicular to the floor, often creating a more modern look. For vertical, the cut boards are at each side wall — if those corners will be covered by trim, waste is lower than if they are exposed.

Gap spacing matters when calculating coverage. The calculator's board-width options already account for standard overlap and nickel-gap specs, but if you plan to leave a custom gap (say, 1/4-inch for a distinct look), you will need slightly more boards to cover the same wall area. Each 1/8-inch of additional gap reduces effective coverage per board by about 2.3% on a 5.5-inch face.

Step 4: Review Results and Cost

The shiplap calculator outputs total linear feet, number of standard 12-foot boards, and optional cost if you enter a price per linear foot (typically $1–$4 for pine, $3–$8 for reclaimed wood, $2–$6 for MDF shiplap). The wall preview diagram shows individual board rows at scale so you can visualize coverage before buying.