Decking calculator
Enter your deck size and board choice to get the lineal metres of decking, the frame timber, stumps, concrete and screws to order.
Your order list
How much decking do I need?
Divide the deck width by the board width plus the gap to get the number of rows, then multiply by the length to get the linear metres of board. A 3.6 m wide deck in 140 mm boards with 5 mm gaps is 25 rows. Add about 10% for cuts, offcuts and staggering the joins.
Buy boards long enough that joins land on joists, and stagger them so they don't line up across the deck.
How the frame goes together
- Stumps or posts set in concrete hold up the bearers.
- Bearers run the length of the deck, usually no more than 1.8 m apart.
- Joists sit across the bearers at 450 mm centres for most timber decking, closer for composite and thin boards.
- Boards are screwed down with two screws at every joist.
These results are estimates to help you plan and order. Joist, bearer and stump sizes and spacings must suit your spans, timber grade and deck height, so check them against the span tables or with an engineer. Decks over 1 m high need a balustrade and usually need approval.