About this calculator
Count deck boards by rows and stock length, the way you would lay them, plus face screws or hidden clips at every joist.
How it’s calculated
Rows = (deck width + gap) ÷ (board width + gap), rounded up. Boards per row = deck length ÷ stock length, rounded up. Screws = rows × joists × 2.
Worked example
With these inputs:
- Deck length (board direction)
- 4.8 m
- Deck width (across boards)
- 3.6 m
- Board width (actual)
- 86 mm
- Gap between boards
- 4 mm
- Board length
- 4.8 m
- Joist spacing
- 450 mm
- Fixing
- Face screws (2 per joist)
- Waste allowance
- 10%
the result is:
- Deck boards
- 46 × 4.8 m
- Deck area
- 17.28 m²
- Linear board
- 196.8 lin m
- Screws
- 984
Tips from the trade
- Choose a board length that divides the deck neatly, or plan the butt joints over doubled joists.
- Picture-frame borders need extra boards: add them as a second calculation.
- 19 mm hardwood decking needs joists at no more than 450 mm centres. Composite boards often need 400 mm or less, especially on diagonals.
- Pre-drill hardwoods such as merbau and spotted gum, and leave boards to acclimatise for a few days. Merbau bleeds tannin when wet, so keep it off pale paving.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the NCC and Australian Standards before ordering.