Deck Board Calculator

Decking Boards

The calculator determines how many board rows fit across the deck width, accounting for the board face width and the gap between boards:

1. Effective board width = board face width + gap
2. Rows needed = deck width ÷ effective board width (rounded up)
3. Boards per row = deck length ÷ board length (rounded up)
4. Total boards = rows × boards per row × (1 + waste%)

Joists

Joists run perpendicular to the decking boards and support the deck surface:

1. Number of joists = (deck length ÷ joist spacing) + 1, rounded up
2. Each joist spans the full deck width
3. Includes a rim joist at each end

Fasteners

• Deck screws / nails: 2 fasteners per board at each joist crossing
• Hidden clips: 1 clip per board at each joist crossing
• A waste factor is applied to the fastener count as well

Tips

• A 10% waste factor is standard; use 15% for diagonal or complex patterns
• 16 in on-center joist spacing is most common for residential decks
• Composite boards typically use hidden clips; pressure-treated lumber uses screws
• Always check local building codes for joist spacing and structural requirements