How Many Boards for an 8x10 Deck?
Deck boards to buy
9 20 ft boards
80 square feet, 17 rows running the 10 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 length10 ft
- Deck width8 ft
- Board face width5.5 in
- Gap between boards0.25 in
- Board length you buy20 ft
- Joist spacing on center16 in
Deck boards to buy9 20 ft boards
| Deck area | 80 sq ft |
|---|---|
| Board rows across the width | 17 |
| Linear feet of decking | 170 lf |
| Boards at 20 ft | 9 |
| Joists at 16 in on center | 9 |
The material list this produces
| Deck boards, 20 ft | 9 |
|---|---|
| Joists, 8 ft | 9 |
| Joist hangers, each | 18 |
| Deck screws, lb | 3 |
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 | 22 8 ft boards |
| 12 ft boards | 15 12 ft boards |
| 16 ft boards | 11 16 ft boards |
| 20 ft boards | 9 20 ft boards |
What else matters here
Seventeen rows at 10 feet, 170 linear feet, nine 20 foot boards cut in half. Nine boards to carry instead of seventeen, and every row a single unbroken piece.
Twenty foot decking is where the theory runs into the truck. A 20 foot board will not fit in a pickup bed, will not go around the side of most houses, and is heavy enough in wet treated lumber that it takes two people to carry without whipping it. Delivery is usually the answer, and delivery has a fee.
Weigh that against 17 boards at 10 feet, which one person can carry and which cost a little more per foot. On a deck this size the difference is small either way, which is exactly why it is worth deciding rather than defaulting: the long boards win on price and lose on handling.
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 an 8x10 deck?
Nine boards of 5/4 by 6 at 20 feet cut in half, or seventeen at 10 feet, both giving 170 linear feet.
Are 20 foot deck boards worth it?
On price usually, on handling rarely. They will not fit in a pickup, they are awkward around a house, and wet treated lumber at that length is a two person carry.
How many joists for an 8x10 deck?
Nine at 16 inches on center along the 10 foot run, each one 8 feet long.
The deck calculator takes any dimensions you like and hands back the same list.