Deck Board Calculator – How Many Boards Do I Need? | CalcLoft
Find out exactly how many deck boards you need for your build.
How many deck boards do I need?
Divide the deck width by the board's face width plus gap. A 10 ft wide deck (120 in) with 5.5-in boards and 1/8-in gaps: 120 ÷ 5.625 ≈ 22 boards, each as long as the deck length — plus 10% for cuts = about 24 boards.
Boards for a 12 ft deck length
| Deck width | 2×4 (3.5 in) | 2×6 (5.5 in) |
|---|---|---|
| 8 ft | ~28 boards | ~18 boards |
| 10 ft | ~35 boards | ~22 boards |
| 12 ft | ~42 boards | ~27 boards |
Don't forget the framing
- Joists: 2×8 or 2×10 at 16 in spacing
- Beams and posts per your deck plan
- Screws: about 2 per board per joist
Deck board calculator FAQ
How many 2x6 boards for a 10x12 deck?
About 22 boards (5.5 in wide, 1/8 gap) plus waste ≈ 24.
What gap should deck boards have?
1/8 inch for pressure-treated, 3/16 inch for composite (thermal expansion).
Do composite boards need special spacing?
Yes — composite expands more with heat, so follow the manufacturer's gap spec.
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