Free tool
Deck Board Calculator
Enter your deck size and board choice to estimate boards, screws, joists, and total material cost. Great for a quick sanity check — for full labor, waste, profit, and proposal export, use the BuildScape estimator.
How this deck board calculator works
Deck board count comes from your deck area divided by the coverage of a single board (actual board width + gap, multiplied by board length), rounded up and padded with a waste allowance. The default 10% is a common cutoff for straight rectangular decks with 12–16 ft boards; picture-frame borders, diagonals, or complex layouts usually need 12–15%.
Joists are estimated at 16" on center — the standard spacing for 5/4" and 2× deck boards. Wider spans, composite manufacturers, or hot-tub loads may call for 12" on center; adjust in your engineering plan.
Fasteners assume roughly two screws per joist crossing on standard 5/4" x 6" boards (~350 screws per 100 sq ft). Hidden-fastener systems, screw shank size, and edge boards can push that number up.
This tool covers the decking surface only. A full deck estimate also includes framing lumber, ledger and beam sizing, footings, posts, railing, stairs, labor, overhead, and profit — all of which BuildScape handles automatically for contractors running real jobs.