Find out how many deck boards, joists, and screws you need. Enter your deck size and board size to get a count.
0boards
| Item | Amount |
|---|---|
| Deck area | |
| Rows of boards | |
| Total board length | |
| Joists | |
| Screws (2 per crossing) |
Decking boards are laid in rows with a small gap. The calculator finds how many rows fit across the deck, how much total board length that takes, and how many boards of your chosen length cover it.
Rows = deck width (in) ÷ (board width + gap), rounded up
Boards = rows × deck length × (1 + waste) ÷ board length, rounded up
Lumber sizes are nominal, so a 5/4 x 6 board is really about 5.5 inches wide, and a 2 x 4 is about 3.5 inches. The calculator uses the real width. Composite boards vary by brand, so check the product's actual width.
Pick a board length that matches your deck so fewer boards need cutting. A 16 foot deck with 16 foot boards has almost no waste, but joints between boards must land on joists, and many builders stagger them. Add more extra if you plan a diagonal or herringbone pattern.
With 5/4 x 6 boards, a 1/8 inch gap, and 10 percent extra, a 12 x 16 foot deck takes about 29 boards of 16 feet, with the boards running the 16 foot direction.
Many builders leave about 1/8 inch for dry or kiln-dried lumber, and a bit more for wet pressure-treated wood that shrinks as it dries. Composite makers specify their own gap, so follow the instructions.
Ten percent for straight layouts. Fifteen percent or more for diagonal patterns or a deck with several corners or cutouts.
Sixteen inches on center is the most common. Some composite decking needs 12 inches, and some wood decking allows 24 inches. Follow your decking manufacturer's guidance and local code.
No. It covers the surface boards, a joist count, and screws. For the footings, a concrete calculator can help. See the fence post concrete calculator for the bag-count approach.