How Many Boards for a 12x12 Deck?
Deck boards to buy
20 16 ft boards
144 square feet, 5/4 by 6 decking at a quarter inch gap, joists 16 inches on center.
When the figures look right, the deck material list downloads as a real PDF with your business details on it, built inside your own browser. Nothing you type is uploaded anywhere.
How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Deck length12 ft
- Deck width12 ft
- Board face width5.5 in
- Gap between boards0.25 in
- Board length you buy16 ft
- Joist spacing on center16 in
Deck boards to buy20 16 ft boards
| Deck area | 144 sq ft |
|---|---|
| Board rows across the width | 26 |
| Linear feet of decking | 312 lf |
| Boards at 16 ft | 20 |
| Joists at 16 in on center | 10 |
The material list this produces
| Deck boards, 16 ft | 20 |
|---|---|
| Joists, 12 ft | 10 |
| Joist hangers, each | 20 |
| Deck screws, lb | 5 |
Board length compared
Same deck, four board lengths.
| Board length | Deck boards to buy |
|---|---|
| 8 ft boards | 39 8 ft boards |
| 12 ft boards | 26 12 ft boards |
| 16 ft boards | 20 16 ft boards |
| 20 ft boards | 16 20 ft boards |
What else matters here
The board count comes from linear feet, not from area. Twelve feet across at five and a half inches plus a quarter inch gap is 26 rows, each 12 feet long, which is 312 linear feet of decking. Cut from 16 foot stock that is 20 boards.
What this calculator assumes
- A nominal 2x6 board is 5.5 inches of actual face. Nominal sizes are not real sizes, which is where most deck orders go wrong.
- Joist count is the span across the deck width at the spacing given, plus one for the last joist.
- Waste is not added. Add 5 to 10 percent if the deck is not a plain rectangle.
Questions people ask
How many deck boards for a 12x12 deck?
About 20 boards of 5/4 by 6 at 16 feet, which is 312 linear feet of decking across 26 rows.
How many joists for a 12x12 deck?
Ten joists at 16 inches on center, plus the rim joists.
The deck calculator takes any dimensions you like and hands back the same list.