Deck Board Calculator Formula
Understand the math behind the deck board calculator. Each variable explained with a worked example.
Formulas Used
Deck Area
deck_area = deck_length * deck_widthBoards Across Width
boards_across = ceil(deck_width / board_coverage_width)Linear Feet of Boards
linear_feet = ceil(deck_width / board_coverage_width) * deck_lengthBoards Needed
boards_needed = ceil(ceil(deck_width / board_coverage_width) * deck_length / board_length * (1 + waste_percent / 100))Variables
| Variable | Description | Default |
|---|---|---|
deck_length | Deck Length(feet) | 16 |
deck_width | Deck Width(feet) | 12 |
board_width | Board Width (nominal)(inches) | 5.5 |
gap | Gap Between Boards(inches) | 0.125 |
board_length | Board Length(feet) | 16 |
waste_percent | Waste Factor(%) | 10 |
board_coverage_width | Derived value= (board_width + gap) / 12 | calculated |
How It Works
How to Calculate Deck Boards
Formula
Boards Across = Deck Width / (Board Width + Gap)
Total Boards = Boards Across × Deck Length / Board Length × (1 + Waste)
A nominal 2×6 deck board is actually 5.5 inches wide. Include a 1/8-inch gap between boards for drainage and expansion. Board lengths come in 8, 10, 12, 14, 16, and 20 ft.
Worked Example
A 16 ft by 12 ft deck with 5.5-inch (2×6) boards, 1/8-inch gaps, 16 ft board length, 10% waste.
deck_length = 16deck_width = 12board_width = 5.5gap = 0.125board_length = 16waste_percent = 10
- 01Board coverage width = (5.5 + 0.125) / 12 = 0.469 ft
- 02Boards across = 12 / 0.469 = 25.6 → 26 boards
- 03Linear feet = 26 × 16 = 416 lin ft
- 04Boards at 16 ft = 416 / 16 = 26 boards
- 05With 10% waste = 26 × 1.10 = 28.6 → 29 boards
Ready to run the numbers?
Open Deck Board Calculator