How the deck board calculator works
Effective width changes the count
A 5.5" board with a 1/8" gap covers 5.625" — across a 12-foot deck that difference adds a full board row. Composite boards with hidden fasteners need exact gaps too. The calculator multiplies rows by length for linear feet because decking is bought by the board, not by area — the unit mismatch that wrecks most first budgets.
Material choices and their math
Pressure-treated pine is the budget baseline (10% waste, annual maintenance). Cedar and redwood cost 2× and resist rot naturally. Composite runs 3–4× pine but orders in exact lengths, hides fasteners, and skips staining forever — the lifetime-cost math (stain gallons × years) closes much of the gap on paper.
Fasteners by the crossing
Two screws per joist crossing means roughly 2.2 fasteners per square foot for standard 16" joist spacing — a 200-sq-ft deck eats ~450 screws. Hidden-fastener composite systems price differently per square foot but install faster. The fastener line is small money with big squeak consequences; do not cheap out.