Decking Board Calculator
Free decking calculator. Estimate deck boards, joists and screws from deck dimensions with board width, gap spacing, board length, joist spacing, waste allowance and cost totals. Simple client-side math.
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What is Decking Board Calculator?
The Decking Board Calculator turns deck dimensions into a material list: how many boards of a given width, gap and purchasable length cover the deck with a waste allowance, how many joists the frame needs at your chosen spacing, how many screws fix every board at every crossing, and what it all costs from your supplier prices. It assumes a straight-run deck with boards parallel to the length, the most common layout.
Key Benefits
- One pass from deck size to a complete board, joist and screw list
- Waste allowance protects the budget from offcuts and mistakes
- Joist count and linear meters straight from your spacing choice
- Cost totals accept your own supplier prices in any currency
- Copyable summary ready to send for quotes
Common Use Cases
- •Planning a garden deck or terrace build from scratch
- •Comparing timber against composite board costs per project
- •Ordering the right amount of material for a decking replacement
- •Checking whether a wider board saves rows and money
- •Pricing joist upgrades like tighter spacing for composite boards
How to Estimate Decking Materials
- Measure the deck: Enter the length and width of the finished deck in meters. Boards are laid parallel to the length; swap the two numbers if you want the boards running the other way.
- Set the board and gap size: Enter the board width in millimeters and the drainage gap between boards, commonly 5 mm for timber and 3 to 6 mm for composites, plus the length your supplier sells.
- Choose the joist frame: Set the joist center-to-center spacing, typically 400 mm for timber or 500 mm for composite boards. The count includes an extra joist at each end.
- Add waste and prices: Allow 10 to 15 percent waste for offcuts, enter the price per board and per meter of joist, and copy the totals for your supplier.
Key Features
- Board count from deck size, board width, gap and purchasable board length
- Waste allowance from 0 to 100 percent with rounding up
- Joist count and linear meters from center-to-center spacing
- Screw estimate from every board-joist crossing
- Cost totals for boards and joists plus a copyable shopping summary