Deck Screw Calculator

About this calculator

The estimate starts from deck area and board width to get the number of boards, multiplies by the number of joists the decking crosses (deck length ÷ joist spacing), and applies the screws-per-crossing count you specify (typically 2 per board-joist intersection) — then divides by a standard box count (usually 100 or 350 screws per box) to round up to whole boxes.

DIY deck builders and contractors use it before a lumber-yard run to avoid the classic mid-project problem of running short on fasteners, and it's especially useful for estimating exterior-grade or coated deck screws, which cost noticeably more per box than general-purpose screws and aren't worth over-buying.