Deck Calculator
Joists, deck boards, footings for any deck
📚 Learn more — how it works, FAQ & guide Click to expand
Learn more — how it works, FAQ & guide
Click to expand
Deck calculator
Calculate deck boards, joists, posts, concrete footings.
How to use this tool
- 1
Enter deck size
Length and width in feet.
- 2
Choose board width
5.5" is most common (actual width of 6" nominal).
- 3
Get material list
Boards, joists, posts, footings, screws.
Frequently Asked Questions
Joist spacing
Standard: 16" on-center. For composite or thicker decking: 12" OC. Code-compliant and stiffer.
Posts and footings
Post every 8 ft along perimeter. Concrete footing 24" deep (frost line varies by region).
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100% Privacy. This tool runs entirely in your browser. Your data is never uploaded to any server.