Rows across, lengths along
Boards run along the deck length. Count how many rows fit across the width using face width plus gap. Then see how many stock lengths you need along each row (butt joints). Multiply and add waste for bad boards and cuts.
Composite and treated lumber stock lengths differ by brand. Enter the length you will actually buy. Framing, joists, and footings are separate — this tool is decking surface only.
Gaps and drainage
Follow the manufacturer gap for composite; wood often uses about 5 mm when dry but local practice varies. Wider gaps change board count. Always check install guides for your product and climate.
Frequently asked questions
- Is the deck calculator free?
- Yes. Free to calculate, print, and share.
- Does it include joists?
- No. It counts surface boards only. Add framing on your quote as a separate package.
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