Deck Calculator
Decking & Fencing · Updated July 2026
Enter your deck dimensions and board size to find how many deck boards you need — with a waste allowance for cuts.
Your project
Results
Estimates only. Add extra for waste and confirm with your supplier.
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How many deck boards do I need?
Divide the deck area by the coverage of one board (board width × length), then add about 10% for waste and cuts.
Counting deck boards
Divide the deck area by the coverage of one board (board width × length), then add 10% for waste — more for diagonal or picture-frame patterns. Remember the small gap between boards slightly increases the count.
Beyond the boards
You'll also need joists, hangers, and fasteners: hidden clips or two screws per joist crossing. A 16-inch joist spacing is standard for most decking; 12-inch is better for diagonal layouts.
How to use this calculator
- 1Measure your deck length and width in feet.
- 2Enter your board width and length.
- 3Set waste % and read the board count.
Frequently asked questions
How much extra decking should I buy?
Add 10% for straight-lay decks and 15% for diagonal or picture-frame patterns.
How many deck boards do I need?
Divide the deck area by one board's coverage (width × length) and add about 10% for waste.
What spacing should deck joists be?
16 inches on center is standard; use 12 inches for diagonal decking.
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