Board count for an 8×10 deck by board length
5.5-inch boards with 1/8-inch gaps, 10% waste.
| Board length | Boards to buy | Total linear ft | Butt joints? |
|---|---|---|---|
| 12 ft | 20 | 240 ft | None — 2 ft offcut per board |
| 16 ft | 20 | 320 ft | None — 6 ft offcut per board |
| 20 ft | 10 | 200 ft | None |
The highlighted length wastes the least lumber for a 10 ft run. Each 20 ft board gives 2 full rows, so there are no butt joints.
Joists and screws
- At 16 in on center: 9 joists spanning 8 ft, about 324 screws (1 box of 350)
- At 12 in on center (composite or diagonal): 11 joists and about 396 screws
Joist size depends on the span, wood species and local code. An 8 ft span is a common size, but confirm joist dimensions with your local building department's span tables.
The math
8 ft × 12 ÷ (5.5 + 0.125) = 17.07 → 18 rows
18 rows × 1.10 waste ÷ 2 rows per 20 ft board = 10 boards
Common questions
How many deck boards for an 8x10 deck?
10 boards of 20 ft (5.5-inch width, 10% waste included).
How many joists for an 8x10 deck?
9 joists at 16 inches on center, or 11 at 12 inches.
How many screws for an 8x10 deck?
About 324 deck screws — two per board at every joist.
Want the full method, tips and other sizes? See the deck board calculator guide.