Decking is priced by the board, not the square metre. Which length your supplier stocks changes the order more than any waste allowance does — and almost no calculator mentions it.
Enter the deck size and the board dimensions. We'll count boards — and show you what the length choice is costing you.
Works in metric and US imperial — you choose at the start and can switch at any time. Every figure this calculator uses is published with its source, and the result comes with a printable order sheet. No account, no email, and nothing you type leaves your browser.
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Which means the length your supplier stocks changes the order more than any waste allowance does. A deck that divides neatly into 3.6 m boards and badly into 4.8 m ones can differ by a noticeable number of boards for exactly the same area. Almost no calculator mentions this; this one shows you what the length choice is costing, so you can ask the yard what they carry before committing.
Leave 3–6 mm between boards — more for timber that arrives wet, less for kiln-dried or composite. Boards laid tight will cup and trap water; the gap is drainage, not tolerance. Joist spacing depends on board thickness and direction, typically 400–450 mm for straight boards and closer for diagonal, and the board manufacturer's figure is the one to follow. Composite deserves particular care: it expands along its length with heat, so end gaps at fixed points matter and the manufacturer's spacing figure is not a suggestion.
Decks are rarely built exactly to plan, so measure what is actually there once the frame is up. Stagger any board joints across the deck and land every one on a joist — a line of joints in a row is the first thing anyone notices. And order a couple of extra boards: timber arrives bowed, split or with a bad face, and the rejects become blocking and stair treads rather than waste.
Usually 3–6 mm — more for timber that arrives wet, less for kiln-dried or composite. The gap is drainage. Boards laid tight cup and trap water underneath.
Typically 400–450 mm for boards laid straight, and closer for a diagonal layout. Check the board manufacturer's figure, because it varies with board thickness and a deck that bounces is usually a spacing problem.
Yes. Composite expands along its length with heat far more than timber does, so end gaps at fixed points matter and the manufacturer's spacing figures are requirements rather than suggestions.
Because decking is sold and priced by the board, not by area. A deck that divides neatly into one stock length and awkwardly into another needs a different number of boards for the same square metreage. Ask what lengths your supplier carries before ordering.