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)
- 144 mm
- Gap between boards
- 5 mm
- Board length
- 4.8 m
- Joist spacing
- 400 mm
- Fixing
- Face screws (2 per joist)
- Waste allowance
- 10%
the result is:
- Deck boards
- 28 × 4.8 m
- Deck area
- 17.28 m²
- Linear board
- 120 lin m
- Screws
- 650
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.
- Composite boards often need joists at 300–350 mm for diagonal layouts.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.