Deck Board Spacing Calculator
Estimate how many equal-width deck boards fit across a span and the resulting equal gap between boards.
Results
Boards across span
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Equal gap
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Use the result as a planning estimate and verify project-specific dimensions and product information before ordering or cutting.
How it works
The calculator chooses enough boards so the equal gap between them does not exceed your maximum gap, then distributes the remaining space evenly.
boards = ceil((span + max gap) ÷ (board width + max gap))Worked example
Across a 10 ft width using 5.5 in boards and a 1/4 in maximum gap, 21 boards give an equal gap of 0.225 in, shown to the nearest 1/32 in.
Assumptions
- Board widths are treated as equal and straight.
Limitations
- Actual installed gaps can change as wood moisture content changes; follow the decking manufacturer's installation guidance.