Deck Calculator
Decking stock boards, cut yield and optional layout counts.
Your project
Enter your measurements. Required fields are labeled; assumptions and optional quotes can be edited below.
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How this calculator works
Enter a rectangular deck surface with boards running along run length, and cross width measured across rows. Supply actual board face width and side gap, usable stock length after any trim/end-clearance decisions, saw kerf and stock allowance. The last row may need ripping. Even a cross width below one board requires one row. Offcuts do not reduce the installed row count.
Area = run × cross width; rows = ceil((cross width + gap) / (board width + gap)); full row pieces/stock = floor((usable stock + kerf) / (run + kerf)); base stock = ceil(rows / pieces per stock); purchased stock = ceil(base stock × (1 + allowance)).Cut yield expresses p × run + (p − 1) × kerf ≤ usable stock. With 6 m stock, a 3 m complete row and positive kerf, only one complete row fits. Stock shorter than a row is unsupported: choose longer usable stock or divide the project into separately designed deck sections. End-joint layouts are outside this tool. Required row-linear length is rows × run. Purchased stock length is purchased boards × usable stock length. Their difference is planning information; it includes reserve and cutting losses and is not a usable-offcut guarantee or cut plan.
Optional joist positions = ceil(run / maximum spacing) + 1, including both end supports; actual equal spacing = run / (positions − 1). Joists run across cross width and receive no automatic waste. Optional face screws require joists. Base screws = installed rows × joist positions × screws/crossing; adjusted screws = ceil(base × (1 + screw allowance)); packs = ceil(adjusted / screws per pack). Spare decking stock does not add screw demand. Costs use purchased decking stock, exact joist positions at the price per cross-width piece, and whole screw packs.
Assumptions and limitations
Layout count only — spacing and spans require an approved design. Surface and stock planning only. Single-piece rows; no end-joint layouts or offcut reuse optimization. Remaining stock length is planning information, not a cut plan. No member sizing, beams, loads, rim/ledger, blocking, posts, footings, overhang or connection design.
US/Metric changes representation only, including inactive fields. Explicit US-market and Metric-market presets change their listed assumptions, never project measurements. Assumptions are editable planning inputs. Required project measurements start blank; calculate explicitly before valid edits update the estimate.
Allowance is the added requirement before whole-item purchase rounding; purchase rounding surplus is separate. Only active supplied prices enter cost. Missing is unpriced, while an entered zero is a valid price. A partial priced list names how many active material types are priced.
Worked examples
DECK-01: Run 12 ft, cross width 10 ft, actual board face 5.5 in, gap 0.1875 in, usable stock 12 ft, kerf 0.125 in and 10% stock allowance. Area is 120 ft², rows 22, pieces/stock 1, base stock 22 and purchased stock 25. Joists at maximum 16 in give 10 positions and actual spacing 16 in. Two screws/crossing, 10% screw allowance and 100/pack give 440 base, 484 adjusted screws and 5 packs. At $20/stock board, $15/cross-width joist piece and $12/screw pack, subtotal is $710.00.
DECK-02: Run 2.4 m, cross width 3 m, actual board 140 mm, gap 5 mm, usable stock 5 m, kerf 3 mm, 10% stock allowance and joists off. Area is 7.2 m²; 21 rows, 2 complete pieces/stock, 11 base and 13 purchased stock boards. Required row length is 50.4 m, purchased stock length 65 m. At $30/stock board, subtotal is $390.00, with no joist or screw line.
Verify actual product gaps, usable stock, manufacturer instructions and the approved structural plan before ordering. Railing, connectors, framing hardware and labor are excluded.