Deck Board Calculator for Decking
Find out how many deck boards a deck needs. Enter the deck length and width, the board face width and length, the gap between rows, and a waste allowance.
How to count deck boards
- Enter the deck length and width in feet.
- Set the board face width and length, plus the gap between boards.
- Add a waste allowance and read off the number of boards to buy.
Examples
12 by 16 ft deck, 5.5 in boards, 16 ft long
L 12, W 16, board 5.5 in by 16 ft, 0.25 in gap, 10% waste
192 sq ft deck, 7.67 sq ft per board, 28 boards
Frequently asked questions
How do I calculate the number of deck boards?
Divide the deck area by the area one board covers, then add waste. A board covers its face width plus the gap, converted to feet, times its length. Rounding up gives the boards to buy.
What board width should I enter?
Use the actual face width, not the nominal size. A nominal 5/4x6 or 2x6 deck board is about 5.5 inches wide, which is the default here. Narrow 1x4 stock is closer to 3.5 inches.
Why does the gap between boards matter?
Boards are spaced so the deck can drain and the wood can move. That gap, often about a quarter inch, means each board effectively covers a little more width, so a small gap lowers the board count.
How much waste should I add for decking?
Around 10 percent suits a simple rectangular deck. Diagonal layouts, picture-frame borders or many short runs waste more, so raise the percentage for a complex pattern or angled deck.
Does this count joists or fasteners?
No. This estimates only the surface decking boards. Framing such as joists and beams, plus fasteners or hidden clips, are sized separately based on your deck plan and local code.
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