How Many Deck Screws Do I Need? Chart by Deck Size
A deck needs two screws at every place a deck board crosses a joist. With 5.5 inch boards and joists at 16 inches on center that is about 396 screws per 100 square feet, so a 12 × 16 ft deck takes about 676 screws. Enter your own deck in the deck board calculator to get the boards, joists and screws together.
Part of the project planner: Planning and building a deck.
Deck screws by deck size
5.5 inch boards (5/4×6 or 2×6) with 1/8 inch gaps. The first number is the length the boards run, the second the width out from the house:
| Deck | Rows of boards | Joists at 16 in | Screws, joists at 16 in | Screws, joists at 12 in |
|---|---|---|---|---|
| 8 × 8 ft (64 ft²) | 18 | 7 | 252 | 324 |
| 10 × 10 ft (100 ft²) | 22 | 9 | 396 | 484 |
| 12 × 10 ft (120 ft²) | 22 | 10 | 440 | 572 |
| 12 × 12 ft (144 ft²) | 26 | 10 | 520 | 676 |
| 16 × 12 ft (192 ft²) | 26 | 13 | 676 | 884 |
| 16 × 16 ft (256 ft²) | 35 | 13 | 910 | 1,190 |
| 20 × 16 ft (320 ft²) | 35 | 16 | 1,120 | 1,470 |
| 20 × 20 ft (400 ft²) | 43 | 16 | 1,376 | 1,806 |
Buy about 5% more for dropped and stripped screws. Boxes are sold by weight and list the piece count, so divide your total by the count on the box. Board counts for these sizes are in how many deck boards do I need, and there are quick answers for a 10 × 10 deck and a 12 × 12 deck.
How joist spacing changes the count
For a 12 × 16 ft deck (192 ft²) with 5.5 inch boards:
| Joist spacing | Joists | Screws | Screws per 100 ft² |
|---|---|---|---|
| 12 in on center | 17 | 884 | 460 |
| 16 in on center | 13 | 676 | 352 |
| 24 in on center | 9 | 468 | 244 |
Composite boards and diagonal layouts usually need joists at 12 inches; check the board maker's span table before you build.
How board width changes the count
Narrow boards mean more rows, and every row needs its own pair of screws at each joist. Same 12 × 16 ft deck, joists at 16 inches:
| Board | Rows | Screws |
|---|---|---|
| 2×4 (3.5 in) | 40 | 1,040 |
| 5/4×6 or 2×6 (5.5 in) | 26 | 676 |
| 2×8 (7.25 in) | 20 | 520 |
The formula
- Rows = deck width in inches ÷ (board width + gap), rounded up.
- Joists = deck length in inches ÷ joist spacing, rounded up, plus one.
- Screws = rows × joists × 2.
Hidden fasteners instead of screws
Edge clips sit in grooves in the side of the boards, roughly one clip at each place a board crosses a joist. For the 12 × 16 ft deck that is about 338 clips, plus face screws for the first and last boards. Clip packs list the square feet they cover; follow the board maker's fastening guide, because the warranty often depends on it.
Screws are not for the frame
Deck screws hold down the boards only. Joist hangers, ledgers, beams and posts need the structural screws, bolts or nails named by the hanger or connector maker and your building code. The deck materials calculator lists the frame, footings and boards; the deck materials list and common deck-building mistakes cover the rest of the job.
Frequently asked questions
How many deck screws do I need for a 10x10 deck?
About 396 screws: 22 rows of 5.5 inch boards, 9 joists at 16 inches, and two screws at every crossing.
How many deck screws for a 12x12 deck?
About 520 with joists at 16 inches on center and 5.5 inch boards.
How many screws for a 16x16 deck?
About 910 with joists at 16 inches and 5.5 inch boards. Joists at 12 inches, often used for composite or diagonal decking, need more.
How many screws per deck board?
Two at every joist the board crosses. A 16 ft board over joists at 16 inches crosses 13 joists, so it takes 26 screws.
How many screws per square foot of decking?
About 4.0 screws per square foot with 5.5 inch boards and joists at 16 inches, and about 4.8 with joists at 12 inches.
What length deck screws should I use?
2 1/2 inch screws are the usual choice for 5/4 (1 inch thick) deck boards, and 3 inch screws for 2× (1 1/2 inch) boards, so the screw goes well into the joist. Use screws rated for treated lumber or the ones the composite maker specifies.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.
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