The calculation
Two questions, two different estimates
Covering a surface and cutting a list of parts are different jobs. Coverage mode divides the area, including your allowance, by one sheet’s area and rounds up. It does not locate seams, avoid small strips, or position edges on supports. Those layout constraints can increase the number of sheets you buy.
Repeated-parts mode fits one rectangular part size in a uniform grid. It includes kerf between adjacent pieces and optionally rotates the entire grid. It produces a feasible arrangement under those assumptions, but does not search mixed orientations or guarantee the minimum possible sheet count.
A coverage example
A 12 × 10 ft surface has 120 square feet. A 48 × 96 in sheet covers 32 square feet. With a 10% area allowance, the estimate is ceil(132 ÷ 32) = 5 sheets. At $45 per sheet, that is $225 before other charges. Without the allowance, the area-only estimate is 4 sheets.
Why area alone can undercount parts
Eight 18 × 24 in parts occupy only 24 square feet in total. That sounds smaller than a 32-square-foot sheet, but shape and saw cuts matter. On a 48 × 96 in sheet with 1/8 in kerf, the selected uniform grid fits 2 parts across at 18 in, and 3 down at 24 in. Six fit, so eight require two sheets. The diagram shows the orientation actually selected by the calculation.
What the grid assumes
The count along an axis is floor((sheet dimension + kerf) ÷ (part dimension + kerf)). This includes only the gaps between adjacent parts; a part ending exactly at a usable sheet edge needs no extra gap beyond the edge. Defective edges, edge trim, directional face grain, finish sanding and machine limitations must be handled separately.
The extra allowance applies to area in coverage mode and to the required piece count in parts mode. An extra 10% on eight parts becomes nine parts. It is a purchasing choice, not a prediction of your project’s waste.
Questions from the workbench
Does this optimize every possible cutting layout?
No. Parts mode compares uniform grids only. Mixed orientations can sometimes fit more pieces. Use the displayed layout as a bounded estimate, not an optimal nesting claim.
Can I mix different part sizes?
Not in this tool. Calculate each repeated size separately; do not simply add fractional sheet results and assume all offcuts can be shared.
Can I use metric sheet sizes?
Convert the dimensions to inches first. One inch is exactly 25.4 mm. Every input is labeled so sheet inches are not confused with coverage feet.
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