Shiplap Calculator

A shiplap calculator estimates how many boards are needed to cover a wall after accounting for the portion hidden by each board's rabbet or overlap. Wall area is height multiplied by width. Each board's effective coverage is its exposed face width in feet multiplied by board length. The calculator increases wall area by the selected waste percentage, divides by effective board coverage, and rounds up to a whole board. If a price is entered, estimated material cost is the rounded board count multiplied by price per board. Exposed width is the most important board measurement. A product sold as a six-inch board may cover only about five or five and one-half inches after the next course overlaps it. Use the manufacturer's stated coverage or measure the installed reveal. Entering nominal width overstates coverage and can leave the project short. Board length should be the actual stocked length being priced, even when pieces will be cut and joined across a wider wall. The board count is an area-based estimate and does not create a row-by-row cutting plan. Installation direction changes how pieces are used. Horizontal layouts need enough linear footage for every course across the wall, while vertical layouts need enough pieces to reach from floor to ceiling. Staggered joints, stud locations, scarf joints, and restrictions on short offcuts can increase waste beyond simple geometric coverage. Sketching the layout alongside the calculation helps identify where full boards and reusable cutoffs fit. A waste allowance covers end cuts, defects, split tongues, color or grain selection, openings, and mistakes. Ten percent is a common planning value for a straightforward rectangular wall. Rooms with many corners, windows, outlets, diagonal details, or matched grain may need more. If boards must be ordered in cartons, bundles, or fixed quantities, round the calculator result up again to the supplier's package size. Material cost here covers boards only. A complete shiplap budget may include furring, house wrap for exterior work, flashing, trim, corner boards, fasteners, adhesive, primer, paint or stain, delivery, tax, tools, and labor. Moisture movement and acclimation requirements vary by wood species and engineered product. Exterior installations also require a code-compliant weather-resistive assembly and drainage details. Measure each wall separately when dimensions or board orientation differ, subtract large openings only when their surrounding cuts will genuinely save material, and combine rounded quantities at the end. Confirm actual product coverage, grade, moisture suitability, fire requirements, fastening schedule, and installation instructions before ordering. This calculator provides a transparent first estimate for comparing products and budgets, while a detailed takeoff should still reflect the selected layout and site conditions.