Boards for a 12 × 12 ft deck, by board length
A 12 × 12 ft deck has room for a dining set and a grill, with space to walk around them. With 5½ in boards and 1/8 in gaps the deck has 26 rows, which is 312 ft of decking before waste. These counts include 10% waste:
| Board length | Boards to buy | Total length bought |
|---|---|---|
| 8 ft boards | 43 | 344 ft |
| 10 ft boards | 35 | 350 ft |
| 12 ft boards | 29 | 348 ft |
| 16 ft boards | 22 | 352 ft |
| 20 ft boards | 18 | 360 ft |
Waste and layout
| Layout | Waste | 12 ft boards | 16 ft boards |
|---|---|---|---|
| Straight, careful installer | 5% | 28 | 21 |
| Straight (typical) | 10% | 29 | 22 |
| Diagonal or picture-frame border | 15% | 30 | 23 |
Joists and screws
Joists run the 12 ft width and are spaced along the 12 ft length.
| Joist spacing | Joists | Screws |
|---|---|---|
| 12 in on center | 13 | 676 |
| 16 in on center | 10 | 520 |
| 24 in on center | 7 | 364 |
That is just the decking surface, for a 144 ft² deck. Posts, beams, footings, ledger, railings and stairs are extra, and a permit is usually required.
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Tools & materials for this project
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Frequently asked questions
How many deck boards for a 12x12 deck?
With 5½ in boards, 1/8 in gaps and 10% waste, you need 29 boards of 12 ft, or 22 boards of 16 ft. That is 26 rows of decking across the 12 ft width.
How many joists does a 12x12 deck need?
At 16 in on center, 10 joists running the 12 ft width. At 12 in it is 13, and at 24 in 7. Joist size and span must follow your local building code.
How many screws for a 12x12 deck?
About 520 screws: two at every joist for each board. Buy a few extra, since they strip and get dropped.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.