Deck Materials Calculator

A deck breaks down into four material groups, and each follows from the footprint. Deck boards run across the joists, so their count is the deck width divided by one board's width plus its drainage gap, rounded up. Joists carry the boards and are spaced on centre along the length, so the joist count is the length divided by the spacing, plus one for the end joist. Screws come from the layout: two at every point where a board crosses a joist, which is the board count times the joist count times two.

Beams carry the joists. On a ledger-attached deck the house side is held by the ledger, and beams pick up the joists at intervals across their span. Set the longest joist run you want between supports, and the tool divides the deck's projection by it to count the beam lines. Every beam runs the length of the deck, parallel to the house.

Enter the deck's length and width, choose your board width, gap, joist spacing, and beam-span limit, and the tool returns the whole list — boards, joists, beams, and screws — plus the linear feet of decking. It is a material count for planning and ordering. It does not size the joists or beams for load; those depend on species, grade, spacing, and span, so confirm member sizes against your local code or a span table before you build.