How many deck boards for a 12x12 deck?
You need 26 deck boards at 12 ft long.
That is 26 rows across the 12 ft span, or 312 linear feet. Buy 344 linear feet to cover the usual 10% for cuts and defects.
A 12x12 deck by the numbers
| Deck area | 144 sq ft |
|---|---|
| Rows of decking | 26 |
| Board length | 12 ft |
| Boards to buy | 26 |
| Decking | 312 linear ft |
| With 10% waste | 344 linear ft |
| Joists at 16 in on centre | 10 |
| Footings | 9 |
| Deck screws | 696 |
Where that number comes from
- 12 ft across × 12 = 144 in to cover
- 144 ÷ 5.625 = 25.6 rows, rounded up to 26
- 26 rows × 12 ft long = 312 linear feet
- Add 10% for cuts and culls = 344 linear feet
Boards run the length of the deck here, so the 12 ft dimension sets board length and the 12 ft dimension sets how many rows you need. Running them the other way swaps the two numbers.
Working to a different size? The calculator takes any dimensions and returns the same figures.
Cutting a 12x12 out of stock lengths
The 12 ft run lands exactly on a 12 ft board: 26 boards, 26 rows, nothing cut and nothing left over. Why running them the other way changes the order.
Nothing longer divides into 12 ft — the next stock size up is 16 ft, which would leave an offcut too short to use as a row. Buy 26 boards at 12 ft and cut nothing.
Order 344 linear feet, not the bare 312 — about 3 spare rows on a 12x12. What the cull rate covers.
Before you order: getting a decking order right.
Other deck sizes
Deck calculator for any size, or all calculators.