Estimate decking boards, joists and fasteners for a rectangular deck so your lumber order is close before you price it.
Decking is estimated by how many board runs fit across the deck width, then converted to linear feet. Joists are counted from the span at your chosen spacing.
This covers the deck surface and joists only — not beams, posts, footings, ledger, railing or stairs. Use it to size a lumber order and firm up the framing plan with a local code check.
Sixteen inches on-center is standard for most decking. Drop to twelve inches on-center for diagonal board patterns or thinner composite boards that need more support, and always follow the board maker\u2019s span table.
Around 5% for a simple rectangular deck laid straight. Diagonal layouts, picture-frame borders and multi-level decks generate more offcuts, so bump that to 10–15% for those.
No. The calculator sizes the decking surface, joists and fasteners. Beams, posts, footings, the ledger board, railings and stairs are separate — those depend on height, load and local code.
About 3/16 inch is typical for pressure-treated boards that will shrink as they dry, and around 1/8 inch for dry or composite boards. The calculator uses a 3/16-inch gap when counting board rows.
The Home Renovation Project Manager rolls every calculator into one budget — room by room, with a shopping list, contractor quote comparison and a live over-budget warning.