How to Calculate Decking
Decking material calculations depend on total deck area, board dimensions, and spacing gaps. Always account for waste from cuts and imperfections.
The Formula
Boards = Deck Area / Board CoverageWhere:
AreaDeck Area — Total deck surface in square feetBoardBoard Coverage — Square feet covered per boardBoardsTotal Boards — Number of boards neededStep-by-Step Example
Here's how to calculate decking step by step:
- 1Calculate deck area: Multiply deck length by width for total square footage.
- 2Determine board coverage: A standard 5.5 in x 12 ft board covers about 5.5 sq ft.
- 3Divide and add waste: Divide total area by board coverage, then add 10-15% for waste.
Following these 3 steps gives you the final decking value.
Skip the Math
A 16x12 ft deck (192 sq ft) using 5.5-inch wide, 12 ft long boards needs about 35 boards, plus 4 extra for 10% waste.
Use the Free CalculatorWhy You Need This Calculation
- Accurate decking estimates prevent costly extra lumber orders and reduce material waste.
Common Mistakes
Using nominal board width instead of actual.
A 2x6 board is actually 5.5 inches wide, not 6.
Forgetting gaps between boards.
Include 1/8 to 1/4 inch spacing in your calculations.
Not adding waste for angled cuts.
Add 15% waste for angled or herringbone patterns.