Calculator · Outdoor builds
Deck Board Calculator
Estimate deck board quantities from deck size, board width, gaps, stock length, layout direction, waste, and optional material costs.
Deck board calculator
Result
Enter deck and board dimensions, then calculate the board estimate.
How it works
This calculator estimates deck board rows and board counts from deck size, board width, gap, board length, direction, and waste. It supports metric and imperial inputs and reports total linear length in both metres and feet.
Use it for early lumber/timber ordering estimates. Borders, breaker boards, stairs, angled layouts, board staggering, and exact seam placement can change the final count.
- If boards run along deck length: board rows = ceiling((deck_width + gap) / (board_width + gap)); linear length needed = board rows x deck_length.
- If boards run along deck width: board rows = ceiling((deck_length + gap) / (board_width + gap)); linear length needed = board rows x deck_width.
- Boards before waste = ceiling(linear length needed / board length).
- Boards after waste = ceiling(boards before waste x (1 + waste_percent / 100)).
- Estimated cost = boards after waste x board price.
Worked example
For a 4.8 m by 3.6 m deck using 140 mm boards with 5 mm gaps, the gap applies only between adjacent rows.
Board rows are ceiling((3.6 + 0.005) / 0.145) = 25. Linear length is 25 x 4.8 = 120 m. If each board is 4.8 m, that is 25 boards before waste.
Common mistakes
- Using nominal board width instead of actual board width.
- Forgetting the planned gap between boards.
- Ignoring borders, breaker boards, stairs, diagonal layouts, and seam patterns.
- Treating the estimate as a final cut plan instead of checking the real deck layout.
Common questions
Does board direction affect the estimate?
Yes. The number of board rows is calculated across the dimension the boards cover, so changing direction can change board count and waste.
Should I include the gap between deck boards?
Yes. The entered gap is applied between adjacent board rows only. No perimeter gap is included, and the last board may need trimming to fit.
Does this include picture-frame borders?
No. Add border boards, breaker boards, stair boards, and special layout details separately.
Can I use this for timber decking and lumber decking?
Yes. Enter the actual board dimensions and the units that match your material.