Frame it right, buy it once.
Enter your deck size and board choice and see the full materials list: how many decking boards and joists you need, the posts and footings under them, the screws to fasten it all, and the total installed cost. Everything updates as you type.
The deck
Your materials list
How the deck breaks down
Boards, joists, posts and screws
Build checklist
Bill of materials
Joist spacing comparison
The same deck framed at different joist spacings. Tighter spacing adds joists and screws for a stiffer, quieter feel; the decking board count stays the same.
| Joist spacing | Joists | Boards | Screws | Posts | Est. cost |
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Deck building, explained
How to Calculate Deck Materials
Start with the total square footage (length x width). For decking boards, divide the deck width by the board width (in feet) to get the number of rows, then multiply by the deck length for total linear feet. Joists run perpendicular to decking boards at 16-inch spacing. Posts are placed every 6-8 feet along the beam.
Choosing Deck Board Sizes
Standard deck boards are 5.5 inches wide (actual dimension of a 2x6). Composite boards come in 5.5-inch and 7.25-inch widths. Board thickness is typically 1 inch (5/4 decking) or 1.5 inches (2x lumber). Add 10-15% waste factor for cuts, especially for diagonal or picture-frame patterns.
Common questions
How many screws do I need for a deck?
Plan for approximately 350 screws per 100 square feet of decking, using 2 screws per joist connection for each board. A 192 sq ft deck (16x12) needs roughly 700 screws. Hidden fastener systems use fewer but more expensive clips.
What joist spacing should I use?
16-inch on-center spacing is standard for most decking materials. Use 12-inch spacing for diagonal decking patterns, composite decking that requires it, or decks with heavy loads. Check your decking manufacturer specifications.
How many posts does a deck need?
Posts should be spaced no more than 6-8 feet apart along the beam, with posts at every corner and beside stairs. A typical 16x12 deck needs 6-9 posts depending on the beam span capacity and local building codes.
Estimates for planning only. Real counts vary with deck shape, board pattern, beam span, railing, stairs and local code. Order a little extra, set footings below the frost line, and pull a permit for any attached deck before you build.