Composite Decking Calculator
Same board-layout math as the Deck Board Calculator, with composite-specific defaults and notes. Straight-run layouts only for now.
Example deck shown — edit any value below
Not the nominal size — measure the board itself.
Check your product's manufacturer spec for the recommended expansion gap.
Recommended boards to purchase
58
- Deck area
- 240 sq ft
- Board rows
- 26
- Boards per row
- 2
- Base board quantity
- 52
- Waste allowance
- 10%
- Total stock board length
- 928 ft
- Estimated material cost
- $493.00
›Calculation details
This estimate assumes each board row is supplied independently. Efficient reuse of offcuts may reduce actual board quantity. Complex layouts may require additional material.
Actual quantity may change because of:
- Butt-joint placement
- Breaker boards
- Picture framing
- Diagonal layouts
- Unusable offcuts
- Manufacturer installation requirements
rows = ceil((144in + gap) / (board width + gap)) = 26
boards/row = ceil(runLength / stock length) = 2
base = rows × boards/row = 52
+waste → recommended = 58
This estimates a straight-run layout only. Picture-frame borders and breaker boards aren't calculated by this version — add extra material for those separately.
How it works
The geometry here is identical to solid-wood decking — rows across the width, boards per row along the length, waste applied once — so this calculator runs on the exact same tested engine as the Deck Board Calculator rather than a second copy of the formula. What's different for composite is worth checking against your specific product: expansion gap requirements, actual board width, and stock lengths often differ by brand and profile.
What's not calculated yet
Picture-frame borders and breaker boards need their own layout math — mitered corners, border board runs, field board trimming — that isn't implemented in this version. If your design uses either, plan for extra material beyond this straight-run estimate.