Decking for a 12×20 Deck
A 12×20 deck is 240 sq ft — about 36 pressure-treated boards (5.5"×16') plus 3 box of deck screws. Adjust board size below for composite or wider boards.
Deck boards
36 boards
Deck area
240 sq ft
Decking boards
36 boards5.5"-wide × 16' PT, incl. 10% waste
Deck screws
3 boxes~840 screws (≈3.5/sq ft)
Decking cost (est.)
$840~$3.50/sq ft pressure-treated
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How this is calculated
Mulch volume = bed area × depth. We convert cubic feet to cubic yards for bulk delivery and to 2-cu-ft bags for the bagged option, so you can compare cost both ways.