MicroCalculatorsDeck Board Calculator
Estimate how many deck boards you need. Boards = deck width ÷ (board width + gap). Deck width is the dimension perpendicular to the boards.
Width of deck (perpendicular to boards).
Nominal 6-in = ~5.5 in actual.
1/8–1/4 in typical for drainage.
Result:
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Deck Board Calculator — FAQ
- Should I buy extra boards for waste?
- Yes. Add 10–15% for cuts and defects.
- Do composite boards need gaps?
- Yes. Composite expands; follow manufacturer spacing (often 1/8–1/4 in).
- How does board width affect cost?
- Wider boards = fewer boards but more material per board. 5/4×6 is common.
How Many Deck Boards Do I Need?
Number of boards is deck width divided by effective board width (board width + gap). A nominal 6-in board is about 5.5 in wide; add 1/4 in gap = 5.75 in per board. For a 12 ft (144 in) wide deck: 144 ÷ 5.75 ≈ 25 boards.
Add 10–15% for waste. Composite boards need gaps for expansion — follow manufacturer specs. Use our Fence Post Spacing Calculator or Concrete Calculator for related projects.
People Also Ask
- How many deck boards do I need?
- What gap should I leave between deck boards?
- How do I calculate deck square footage?
Want to learn more?
Read our full guide: How Many Deck Boards Do I Need? — board widths, gap spacing, waste by layout, and composite vs wood.
Last updated: February 2026