How the calculator works
Decking is rows: rows = deck width ÷ (board width + gap), rounded up. Total linear footage is rows × deck length, plus 10% for cutoffs and culled boards, converted into the board length you're buying. Screw count uses the standard two fasteners per board at every 16″-spaced joist, about 3.5 screws per square foot.
Worked example: a 16 × 12 deck with 5.5″ boards and ¼″ gaps: 12×12 ÷ 5.75 = 26 rows × 16 ft = 416 linear ft + 10% = 458 ft → 29 sixteen-foot boards and roughly 670 screws.
Buying smart
- Match board length to deck length when possible. A 16 ft deck decked with 16 ft boards has zero butt joints and near-zero waste. Mixed lengths on staggered joints look good but add 5% waste.
- Wood gaps: gap pressure-treated boards ⅛–¼″; green (wet) treated lumber can be laid nearly tight, since it shrinks a gap on its own as it dries.
- Composite: follow the manufacturer's gap spec exactly (usually 3/16–¼″ side, ⅛″ end). Thermal movement is real and warranty inspectors check.
- Fasteners: coated deck screws for treated lumber; stainless near pools and coasts; hidden-clip systems for grooved composite (~90 clips per 100 sq ft).
A note on framing
This tool assumes the frame exists. Joist size, beam spans, and footing diameter are structural questions answered by span tables and your local building department. A deck permit is one of the cheaper insurance policies in DIY.