Deck Calculator
Estimate decking boards, optional joists and fasteners for one or more rectangular deck sections.
Planning note
Board layout matters
The calculator lays full-length stock along the board-run direction, rounds each row up to whole boards, then adds the allowance you choose.
Boards per row = deck length ÷ stock length
Joist stock is an estimating aid only. Beams, posts, footings, blocking, ledgers, rim boards and structural hardware are not included.
Can offcuts be reused?
Often, yes. This calculator intentionally rounds conservatively and then applies your allowance. A detailed cut plan may reduce the final quantity.
Does this design the deck structure?
No. Joist spacing and stock quantities are planning estimates, not structural design. Confirm spans, loads, footings, connections and local code requirements.
Real-world project example
How many deck boards for a 12 × 16 ft deck?
A rectangular 12 × 16 ft deck has a 192 sq ft footprint. To estimate decking rows across the 12 ft direction, assume a nominal 6-inch board with an actual 5.5-inch width and a 0.125-inch gap: each row covers 5.625 inches, so 144 ÷ 5.625 = 25.6, rounded up to 26 rows. If each row runs 16 ft, the nominal running length is 416 linear feet before cuts, seams or waste.
Before you buy materials
Board layout, joist spacing, spans, railings, stairs, framing connections and code requirements are project-specific. Always use the manufacturer’s fastening and spacing instructions.
Adjust the measurements, waste allowance and purchase options in the calculator above to estimate your own project; examples are for planning only.
Project guide: Board feet in ten nominal 2 × 6 × 8 boards →