Deck Board Calculator
SI
Imp
Imperial
Inputs
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Deck length
(L)
Length in the direction the decking boards run.
ft
Deck width
(W)
Width covered by side-by-side board rows.
ft
Board width
(b)
Actual board face width, not nominal size.
in
Board gap
(g)
Planned gap between installed boards.
in
Stock board length
Length of one purchased deck board.
ft
Waste allowance
Extra boards for cut waste, defects, layout changes and attic stock.
%
Joist spacing
On-center joist spacing used for the screw count estimate.
in
Screws per board per joist
Typical decking uses two screws per board at each joist line.
screws
Cost per board
Optional unit price for material-cost estimate.
$/board
Results
Default result
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Boards to buy
29
boards
Rounded up after the waste allowance.
Also computed
Deck area
192
ft²
Board rows
26
rows
Boards per row
1
boards
Linear decking with waste
457.6
ft
Estimated screws
744
screws
Joist lines crossed
13
lines
Board material cost
522
$
Board plus gap coverage
5.687
in
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Method notes
3 notes
Board rows = ceil((deck width + gap) / (board width + gap)). Boards per row = ceil(deck length / stock board length).
The screw estimate counts board rows crossing joist lines and applies the same waste factor. Splices, picture-frame borders, breaker boards and stair treads need a separate layout check.
This is a material takeoff only. It does not size joists, beams, posts, ledgers, guards, stairs, footings, lateral bracing or connections.
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