Actual board width plus the required gap determines row count. Manufacturer instructions and moisture condition determine spacing.
Use actual dimensions
A nominal 1×6 wood deck board is commonly about 5.5 inches wide, while composite profiles vary. Measure or verify the selected product. Add the required gap to the actual board width before calculating how many rows cross the deck.
Wood changes dimension with moisture. Composite and PVC systems respond to temperature and often have product-specific end-gap and fastening requirements. Follow the current installation guide for the exact product.
Layout changes quantity
Picture-frame borders, breaker boards, diagonal fields, stairs, fascia, skirting, and built-in features add boards and cuts. Draw these elements to scale. Decide where butt joints land and whether the framing supports the intended pattern before ordering.
The structure remains controlling
A decking calculator does not verify joist size, spacing, spans, ledger attachment, guards, stairs, footings, or lateral connection. Use an approved plan and local requirements. The American Wood Council’s DCA 6 is a useful prescriptive reference where accepted, but local adoption and project conditions control.
Sources & further reading
References behind this guide
These sources support safety, measurement, or industry context. Product instructions, approved plans, and local requirements control your project.