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Decking Calculator

Enter the deck area and board size to see how many boards you need.

Estimate the decking boards for your project. Enter the deck area and your board length and width, and the calculator works out how many boards you need, adding 10 percent for cuts and the expansion gaps between boards. Remember to budget separately for the sub-frame joists, posts, and the screws or hidden clips to fix it all down.

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Frequently asked questions

Why add a gap between boards?

Timber decking expands and contracts with moisture, so a small gap (around 5 to 8 mm) prevents warping and lets water drain. The 10 percent allowance covers this and offcuts.

What else do I need besides boards?

A joist sub-frame, posts or a solid base, weed membrane, and appropriate decking screws or clips. Treat cut ends of timber with preservative.