Lumber calculator

A zero board width is rejected with invalid_input instead of a divide-by-zero. The same pure arithmetic powers the free browser tool and the API path, so a Saturday sketch matches the line a purchasing script posts later.

How board count and waste allowance are computed

Treat the area as a rectangle whose boards run along the length and whose faces pack across the width. Keep every linear input in one system: if the area is in feet, board length, board width, and spacing are feet; if the area is in metres, those edges are metres. Because the last board has no trailing gap, n boards and n minus one gaps must cover the width, which rearranges to n equals (width plus spacing) divided by pitch. A sixteen-by-ten rectangle with eight-unit boards, a half-unit face, one-hundredth spacing, and ten percent waste packs twenty boards across and two along for a net of forty, four extra boards, a purchase count of forty-four, and a waste allowance of sixteen square units. The path is deterministic floating-point arithmetic with no random seeds, no wall-clock timestamps, and no network. Zero spacing is a legal butt-tight layout; a zero board width is not, because pitch would vanish and the count would be undefined. The pitch of one board plus its following gap is board_width plus spacing. That exact ratio is boards_across_exact; boards_across is the ceiling, so a leftover strip still costs a whole extra board in that direction. Along the run, stock boards are butted end to end with no extra gap: boards_along is the ceiling of length divided by board_length. The net packed count is boards_across times boards_along. Waste percent then adds whole extra boards: waste_allowance_boards is the ceiling of net times waste_percent over one hundred, and board_count is net plus those extras. Waste allowance is purchased face area minus the rectangle: board_count times board_length times board_width, minus length times width. That figure is the extra wood you pay for because you cannot buy a fraction of a board, you rip the last face, you cut ends, and you asked for a percent overage.

What you send, which units apply, and how errors behave

Send six required finite numbers. length is the area dimension along the boards; rows of stock are joined until they span that run. width is the area dimension across the boards, the direction you fill with faces and gaps. board_length is the stock length of one piece, not the finished run: an eight-foot board against a sixteen-foot wall needs two pieces per row. board_width is the actual face width in the same units as width, not a nominal stamp on the end grain: six-inch stock is 0.5 if you work in feet, or 0.1524 if you work in metres. spacing is the intended gap between adjacent faces; zero is allowed when boards are butted. waste_percent is the extra whole-board allowance as a percentage of the net packed count, from zero through one hundred; ten is a common carpentry starting point for covering work. Missing fields, empty strings, non-numeric text, NaN, and Infinity fail with invalid_input naming the field and are not charged. A board_width of exactly zero fails with a message that board width cannot be zero. Non-positive length, width, or board_length, a negative board_width, a negative spacing, and a waste percent outside zero to one hundred fail the same way. On success the JSON echoes the cleaned inputs, the rectangle area, pitch, the exact and whole across and along counts, board_count_net, waste_allowance_boards, the purchase board_count, purchased_face_area, waste_allowance, coverage_width, coverage_length, extra_width, extra_length, plus a unit_note, a formula string, and method lumber_cover_pack so logs can document the algorithm. API pricing is the published base of $0.002 per successful item; validation failures do not consume prepaid balance.

Where a lumber covering calculator earns its keep

Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance. Keep requests small, pin board_count and waste_allowance in tests, and you get a reproducible takeoff for quotes, purchase orders, and edge workers without standing up a CAD kernel of your own.