Deck Board Calculator
A deck board calculator finds how many decking boards you need by dividing the deck area by the coverage of one board (its width times length), then adding waste for cuts and the perimeter. Enter your deck dimensions and board size below to get the board count.
Enter deck dimensions to see the materials.
How Many Deck Boards Do You Need?
To find deck boards, calculate the deck area, then divide by the coverage of one board. A 5.5 inch wide, 12 foot board covers about 5.5 square feet. A 14 by 14 foot deck (196 square feet) needs about 36 boards, or 40 with 10 percent waste. The calculator handles any board size and adds waste, which is important because perimeter cuts and the picture-frame border consume extra boards.
Should You Account for Board Gaps?
Yes. Deck boards are installed with a small gap (about 1/8 to 1/4 inch) between them for drainage and expansion, which slightly increases the coverage per board and is built into standard estimates. The calculator uses the nominal board coverage, which already reflects normal spacing. For wider gaps or diagonal patterns, add a little extra, since diagonal layouts waste more at the edges.
Related calculators
Frequently asked questions
- How many deck boards do I need?
- Divide the deck area by the coverage of one board and add 10 percent waste. A 14 by 14 foot deck needs about 40 of the 5.5 inch by 12 foot boards.
- Do deck boards have gaps?
- Yes, about 1/8 to 1/4 inch between boards for drainage and expansion. Standard coverage estimates already account for normal spacing.