Deck Board Calculator

Number of deck boards for a rectangular deck, accounting for board width and gap.

Formula

Rows = ⌈width(in) ÷ (board width + gap)⌉; boards = rows × ⌈deck length ÷ board length⌉ × (1 + waste%).

Worked example

Inputs: Deck length (board direction) = 16 ft; Deck width = 12 ft; Actual board width = 5.5 in; Gap between boards = 0.1875 in; Board length = 16 ft; Waste allowance = 10 %.

Rows	26
Boards	29
Linear ft	416

FAQ

Why 5.5 in?

A nominal 6 in (5/4×6 or 2×6) board is actually about 5.5 in wide. Measure your boards.

What gap should I use?

Follow the decking manufacturer's installation instructions.

Sources

Geometry (volume/area formulas); no external constant needed

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<p style="font-size:12px">Calculator by <a href="https://provenplaza.com/deck-board-calculator/">Proven Plaza</a></p>

Last reviewed 2026-10-11.