Deck Board Quantity Calculator
Quickly estimate how many deck boards you need by comparing the total deck surface area to the coverage of a single board, including spacing gaps. Planning quantities in advance helps you budget accurately and minimise job-site waste.
Round up and add spare boards for best results.
Examples
- 6.2 × 4.8 m deck using 2.4 × 0.145 m boards ⇒ 85.13 ⇒ order 86 boards
- 5 × 5 m deck with 3.0 × 0.14 m boards ⇒ 59.52 ⇒ round up to 60 boards
- 7.5 × 3.6 m deck with 4.2 × 0.16 m boards ⇒ 39.06 boards before adding wastage
FAQ
Does this include wastage?
The calculation gives the theoretical count. Add 5–15% more boards to cover cuts, defects, and future maintenance.
Assumes boards span the deck length?
Yes. If your boards must be spliced over multiple joists, calculate each run separately and combine the totals.
How do I account for diagonal layouts?
Increase the total board count by roughly 15% for 45° layouts, or compute the coverage using the projected area along the board direction.
Can I work in feet and inches?
Yes. Convert each measurement to metres first or adapt the formula using feet consistently for all dimensions.
Additional Information
- Multiply the raw result by 1.05–1.15 to allow 5–15% extra boards for offcuts, defects, and future repairs.
- If boards will run perpendicular to joists, use the joist-to-joist distance for deck width and include any picture framing.
- Plan board joints so that seams land on joists; staggering joints may require additional boards beyond the base estimate.
- For composite decking, check the manufacturer’s installation guide for exact spacing requirements before ordering.