Decking calculator
Work out how many deck boards, joists, pads and screws you need for a timber or composite deck, plus the board cost — in metric or feet and inches.
Your estimate
Deck boards
29
- Deck area
- 192 ft²
- Rows of boards
- 26
- Total board length (incl. extra)
- 458 ft
- Joists
- 13
- Total joist length
- 156 ft
- Deck screws
- 676
- Board cost
- $725
Estimates for planning only — not a quote, survey or financial advice.
How this is calculated
Formula
- Rows = deck width ÷ (board width + gap), rounded up
- Total board length = rows × deck length × (1 + extra %) · boards = total ÷ board length, rounded up
- Joists = deck length ÷ joist spacing, rounded up, + 1 · each joist spans the deck width
- Pads = joists × (deck width ÷ pad spacing + 1) · screws = rows × joists × screws per crossing
Assumptions
- Boards run along the deck length and joists across it. Rim joists, noggins, posts and footings are not included.
- Joist spacing depends on the board: many timber and composite boards need joists at around 40 cm (16 in) centres or closer — use the board manufacturer's figure, especially for composite decking and diagonal laying.
- Raised decks, decks on roofs or balconies and anything that carries a structural load need a design that meets local building rules; in some areas a raised deck needs permission.
- Board sizes and the price are examples — use the figures from your supplier.