A 4 × 5 m deck with 140 mm boards running along the 4 m side takes about 154 linear metres; a 12 × 16 ft deck with 5½ in boards takes about 449 linear feet.
| Deck (m) | 89 mm boards (lin. m) | 140 mm boards (lin. m) | 184 mm boards (lin. m) |
|---|---|---|---|
| 3 × 3 | 106 | 69 | 53 |
| 3 × 4 | 142 | 92 | 73 |
| 4 × 4 | 189 | 123 | 97 |
| 4 × 5 | 238 | 154 | 119 |
| 5 × 5 | 297 | 193 | 149 |
| 5 × 6 | 352 | 231 | 176 |
| 6 × 6 | 422 | 277 | 211 |
| 6 × 8 | 568 | 370 | 284 |
How it is computed
Rows = deck width ÷ (board width + gap), rounded up; linear length = rows × deck length × 1.10. The first dimension is the direction the boards run. Gaps are 5 mm (metric) or 3/16 in (imperial). Divide by the board length you buy to get a board count.
FAQ
Which way should the boards run?+
Usually across the joists and parallel to the house. Choose the deck length so the boards match stock lengths and butt joints fall on joists.
What gap should I leave between boards?+
About 5 mm (3/16 in) for most wood and composite boards; follow the manufacturer for composite, which also needs end gaps.