Formula
How the decking estimate works
- Board rows = deck width ÷ (board width + board gap), rounded up
- Linear decking = board rows × deck length × (1 + waste %)
- Full boards = linear decking ÷ board length, rounded up
Free project planning tool
Decking calculator
Estimate deck surface area, board rows, total linear length, full board quantity, waste, and material cost.
✓ Metric & imperial✓ Transparent assumptions✓ No signup
Boards & coverageInstant estimate
Example calculation
A 16 × 12 ft deck using 5.5 in boards with a 0.25 in gap needs about 26 rows. With 10% waste and 16 ft boards, the estimate rounds up to 29 full boards.
Planning tips
- Enter the actual face width of the board, not its nominal product name.
- Board direction, breaker boards, picture frames, and staggered joints affect layout.
- Calculate stairs, fascia, railings, framing, and fasteners separately.
Common questions
Decking calculator FAQ
Does the calculator include board gaps?
Yes. The board-row estimate uses both the actual board width and the installation gap you enter.
How much decking waste should I allow?
Ten percent is a useful starting point for a simple rectangular deck. Diagonal boards, picture framing, and complex cuts usually need more.
Does this calculate deck framing?
No. It estimates surface decking boards only. Joists, beams, posts, footings, stairs, railing, fascia, and fasteners require separate planning.