Updated October 2026
How many decking boards do I need?
With a 5 mm gap: 140 mm boards need 6.9 lineal m per m²; 180 mm boards need 5.4 lineal m per m²; 88 mm boards need 10.8 lineal m per m². Add 5–10% for offcuts and divide by the board length.
The formula
Lineal metres = deck area (m²) ÷ (board width + gap, in metres). For 140 mm boards: 1 ÷ 0.145 = 6.9 m per m².
Boards for common deck sizes (10% waste, 5.4 m boards)
| Deck | 140 mm | 180 mm | 88 mm |
|---|---|---|---|
| 3 × 2.4 m | 11 | 8 | 16 |
| 3 × 3 m | 13 | 10 | 20 |
| 4 × 3 m | 17 | 14 | 27 |
| 5 × 4 m | 29 | 23 | 44 |
| 6 × 4 m | 34 | 27 | 53 |
| 8 × 5 m | 57 | 45 | 88 |
| 10 × 6 m | 85 | 67 | 132 |
Clips and joists
One hidden clip where each board crosses a joist. At 350 mm joist spacing that's about 20 clips per m² for 140 mm boards and 31 for 88 mm boards.
Questions
How many lineal metres of decking per m²?
140 mm boards: 6.9 m; 180 mm boards: 5.4 m; 88 mm boards: 10.8 m (5 mm gap).
How many boards for a 3 × 3 m deck?
13 × 140 mm, 10 × 180 mm, 20 × 88 mm boards of 5.4 m, with 10% waste.
Should boards run the long way?
Usually. Fewer joins and less waste, as long as joins land on a joist.
Pricing a deck? Count the boards, see the price list or get free samples.