Deck Material Calculator
Enter the deck size and the board and framing choices you plan to use. You get a shopping-list count for decking boards, joists, screws, footings and rim board.
This is a quantity estimate for a simple rectangular deck. It does not size the framing members or footings; span tables, loads and local code decide that. Add stairs, railing and any ledger separately.
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Worked example
Inputs: deck length 16 ft; deck width 12 ft; decking board width 5.5 in; decking board length you buy 16 ft; gap between boards 0.125 in; joist spacing, on center 16 in; beam lines 2; spacing between posts along a beam 8 ft; waste allowance 10.
- Board rows across 12 ft: 144 in ÷ (5.5 + 0.125) = 25.6, round up to 26 rows.
- Decking length: 26 rows × 16 ft = 416 linear ft; plus 10% waste = 457.6 ft; ÷ 16 ft boards = 28.6, round up to 29 boards.
- Joists: 16 ft = 192 in ÷ 16 = 12 spaces, so 13 joists, each 12 ft long (12 ft boards).
- Screws: 26 rows × 13 joists = 338 crossings × 2 screws × 1.05 spare = 710.
- Footings: 2 beam lines × (16 ÷ 8 = 2 spans + 1 post) = 6 footings.
- Rim board: 2 × (16 + 12) = 56 linear ft.
Result: 29 decking boards to buy.
Where the formula comes from
Standard deck takeoff counting (rows from board width plus gap, on-center joist layout, two fasteners per board-joist crossing). Joist size and span, footing size, and fastener type come from your decking manufacturer, the span tables in IRC Section R507, and local code.
Estimates only. Results are planning figures, not engineering or code advice. Check your local building code and confirm quantities with your supplier.
Frequently asked questions
Does this include stairs and railings?
No. It covers the rectangular deck surface and frame. Stair stringers and baluster counts have their own calculators on this site.
Why does the board count include waste?
Cuts, end trimming and defects use up material. 10% is a common allowance; use more for diagonal patterns or picture-frame borders.
What joist board length should I buy?
The result rounds up to the next standard length that spans the deck width, so you cut to fit. Check availability at your supplier.
Are these footings sized for my deck?
No, only counted. Footing size, depth and frost depth depend on loads, soil and local code. See the deck footing concrete calculator for volume once you know the size.