How Many Boards for a 6x8 Deck?
Deck boards to buy
13 8 ft boards
48 square feet, 13 rows running the 8 foot way, joists 16 inches on center.
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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 length8 ft
- Deck width6 ft
- Board face width5.5 in
- Gap between boards0.25 in
- Board length you buy8 ft
- Joist spacing on center16 in
Deck boards to buy13 8 ft boards
| Deck area | 48 sq ft |
|---|---|
| Board rows across the width | 13 |
| Linear feet of decking | 104 lf |
| Boards at 8 ft | 13 |
| Joists at 16 in on center | 7 |
The material list this produces
| Deck boards, 8 ft | 13 |
|---|---|
| Joists, 6 ft | 7 |
| Joist hangers, each | 14 |
| Deck screws, lb | 2 |
Board length compared
Same deck, four board lengths. Longer boards mean fewer end joints and more offcut risk.
| Board length | Deck boards to buy |
|---|---|
| 8 ft boards | 13 8 ft boards |
| 12 ft boards | 9 12 ft boards |
| 16 ft boards | 7 16 ft boards |
| 20 ft boards | 6 20 ft boards |
What else matters here
Thirteen rows, each a single 8 foot board, 104 linear feet in total. No cuts on the field boards.
The quarter inch gap in that calculation is the right gap for dry decking and the wrong gap for wet treated lumber. Pressure treated boards come off the truck soaked and they shrink as they dry, commonly an eighth of an inch across the face and sometimes more, so a quarter inch gap installed wet becomes three eighths or better within a season.
The rule most deck builders use is to butt wet treated boards tight, or close to it, and to gap dry or kiln dried after treatment boards a quarter inch. Composite is different again and the gap is whatever the manufacturer's instructions say, because their expansion is along the length rather than across the width.
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 6x8 deck?
Thirteen boards of 5/4 by 6 at 8 feet, one per row, no cutting on the field.
How much gap should be left between deck boards?
About a quarter inch for dry lumber. Wet pressure treated boards should be butted tight or nearly so, because they shrink as they dry and open the gap themselves.
Do composite boards need a different gap?
Yes, and it comes from the manufacturer's instructions. Composite moves along its length rather than across its width, so the end gaps matter more than the side ones.
The deck calculator takes any dimensions you like and hands back the same list.