How this calculator works
Effective board width = board width + gap. Linear run needed = (deck area x waste factor) / effective board width. Boards = round up(linear run / board stock length).
Worked example
A 4 m x 3 m deck (12 m2, 10% waste = 13.2 m2) with 145 mm boards and a 5 mm gap needs about 88 m of board run - 25 boards at 3.6 m stock length.
Assumptions to check
- This calculates decking boards only - joists, bearers, footings, and span/spacing engineering are out of scope (a structural question, not a material-quantity one).
- Boards run in one direction across the full deck length; deck patterns (herringbone, diagonal) need extra waste.
- Fixings (screws, hidden clips) are not included.