How Many Boards for a 20x30 Deck?
Deck boards to buy
63 20 ft boards
600 square feet, 42 rows running the 30 foot way, 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 length30 ft
- Deck width20 ft
- Board face width5.5 in
- Gap between boards0.25 in
- Board length you buy20 ft
- Joist spacing on center16 in
Deck boards to buy63 20 ft boards
| Deck area | 600 sq ft |
|---|---|
| Board rows across the width | 42 |
| Linear feet of decking | 1,260 lf |
| Boards at 20 ft | 63 |
| Joists at 16 in on center | 24 |
The material list this produces
| Deck boards, 20 ft | 63 |
|---|---|
| Joists, 20 ft | 24 |
| Joist hangers, each | 48 |
| Deck screws, lb | 18 |
Board length compared
Same deck, four board lengths.
| Board length | Deck boards to buy |
|---|---|
| 8 ft boards | 158 8 ft boards |
| 12 ft boards | 105 12 ft boards |
| 16 ft boards | 79 16 ft boards |
| 20 ft boards | 63 20 ft boards |
What else matters here
Six hundred square feet, 1,260 linear feet of decking, sixty three 20 foot boards with one joint per row.
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 boards for a 20x30 deck?
Sixty three boards of 5/4 by 6 at 20 feet, covering 42 rows of 30 feet each with one joint per row.
The deck calculator takes any dimensions you like and hands back the same list.