Decking Calculator
Estimate decking board quantities for a rectangular deck.
Enter the measurements and press Calculate.
How the decking calculation works
The deck area is divided by the effective board coverage width, which includes the selected gap, to estimate total linear metres. That is converted to full board lengths and a waste allowance is added.
Board spacing
Suitable gaps depend on the decking material, moisture content and manufacturer instructions. Composite and timber products can have different spacing requirements.
This calculator estimates deck-board quantities only. Joists, beams, posts, fixings, structural design and support spacing are not included.
Frequently asked questions
Does board direction matter?
Yes. The area method gives a useful purchasing estimate, but exact board count can change depending on which way boards run and where cuts fall.
Can I use this for composite decking?
Yes, provided you enter the actual board width, board length and the installation gap specified by the manufacturer.