Decking Calculator
Enter your deck dimensions and board choice, the calculator works out the exact number of boards, joists, posts and screws you need, draws your deck, and estimates the total cost.
| Decking boards (140mm hardwood) | 35 lengths | $1,663 |
| Joists | 15 | |
| Bearers | 4 | |
| Posts / footings | 10 | |
| Decking screws | ≈840 | |
| Substructure & fixings | $1,482 | |
| Installation labour | $3,840 |
How we estimate this
The number of decking boards depends on your deck area, board width and the gap between boards. This calculator allows ~10% for cutting waste and works out the supporting joists, bearers and posts as well.
Pricing reviewed: October 2026.
Decking prices by city
Costs vary by city. See the local breakdown for your capital.
Doing more than just decking?
Build a combined estimate across every part of your project in one place.
Pricing reviewed October 2026. Indicative Australian costs, not a quote.
Understanding deckings in Australia
The number of decking boards depends on your deck area, board width and the gap between boards. This calculator allows ~10% for cutting waste and works out the supporting joists, bearers and posts as well.
Hardwood and composite boards cost more per metre than treated pine but last longer. The bill of materials helps you price up a job or check a quote.
Frequently asked questions
How many decking boards do I need?
It depends on the deck size, board width and gap. As a guide, 140mm boards with a 4mm gap cover about 7 lineal metres per square metre. The calculator works out the exact count plus waste.
How far apart should deck joists be?
Joists are commonly spaced 450mm apart for residential decks, closer for some composite boards. Always check the board manufacturer’s span requirements and Australian standards.
How much does decking cost per square metre?
Decking typically costs $200–$350 per square metre installed in 2026, depending on material. The calculator separates materials, substructure and labour.
Are you a renovation business?
Everyone on this page is working out what decking costs because they are ready to hire. Put your business right beneath the calculator, in your state, so you are who they find. From $100/mo.