Decking Calculator
Estimate deck boards and screws needed from deck length and width.
Boards needed
24 boards
- Deck area
- 120 sq ft
- Screws (est.)
- 420
How we calculate this
Total linear feet of boards = deck area ÷ board width (in feet). Boards needed = total linear feet (plus waste) ÷ board length. Screws are estimated at roughly 350 per 100 sq ft, a standard contractor rule of thumb.
Example
Measuring tips
Measure the deck's length and width at the decking surface, and check the actual board width (5.5in for standard 2×6 decking — composite boards vary by brand, so check the spec sheet). Running boards the long way reduces seams and waste.
Common mistakes
- Not accounting for board gaps (typically 1/8 to 1/4 inch), which slightly increases coverage per board.
- Forgetting picture-frame or diagonal layouts add significant waste over a straight run.
- Underestimating fasteners — hidden clip systems and screws have different coverage rates.
Frequently asked questions
How many deck boards do I need for a 12x12 deck?
A 12x12 deck is 144 sq ft. With standard 5.5in boards at 12ft lengths and 10% waste, expect roughly 26 boards — use the calculator above for your exact board size.
How many screws per deck board?
Roughly 2 screws per joist crossing, with joists typically 16 inches on center — this works out to about 350 screws per 100 sq ft of decking.
Related calculators
Estimates are provided for planning purposes. Actual material requirements may vary based on supplier specifications, compaction, site conditions, installation method, waste, and local code.