Deck Calculator
Estimate stock decking boards, board courses, joists and fasteners for a rectangular deck. Adjust actual board width, gap, stock length, joist spacing and waste.
How this calculator works
The calculator divides deck width by board width plus gap to count courses. It converts those courses to linear decking, adds waste, and divides by stock length.
Formula: boards = ceil(courses × deck length × (1 + waste) ÷ stock length)
Worked example
For a 16 ft by 12 ft deck using 5.5 in boards with 1/8 in gaps, the tool counts the rows, adds 10% waste and rounds up to whole stock boards.
Before you order
- Confirm the decking manufacturer’s maximum joist spacing.
- Plan butt joints and breaker boards before ordering stock lengths.
- Footings, beams, ledgers and structural sizing require local-code design.