Decking Board Calculator
Buy Decking Board at Home Depot →How this calculator works
A standard composite decking board (5.5 in wide × 12 ft long) covers 5.5 square feet of deck surface. This calculator divides your total deck area by that coverage figure to get the number of boards, rounding up since boards are sold as whole units.
Formula: Boards = Deck area (sq ft) ÷ 5.5 sq ft per board.
Worked example
An 11 ft × 10 ft deck (110 sq ft):
- Boards: 110 ÷ 5.5 = 20.0 boards
- At $25/board, that’s $500.00 before waste.
- With 10% waste added: 22.0 boards, or $550.00.
Coverage reference
| Deck area | Boards needed |
|---|---|
| 110 sq ft | 20 boards |
| 220 sq ft | 40 boards |
| 330 sq ft | 60 boards |
How to measure your deck
Measure the full deck surface length and width. For decks with an irregular shape (L-shaped, wraparound), break it into rectangles, calculate each separately, and add the board counts together.
Frequently asked questions
How many deck boards do I need?
This calculator assumes a standard composite decking board — 5.5 inches wide and 12 feet long, covering 5.5 square feet of deck surface. Enter your deck's area and it converts directly to board count.
What if my boards are a different width or length?
The default 5.5 sq ft per board matches common composite decking. If your boards are a different size, divide your deck area by your board's actual width (in feet) times its length to get a more precise count, then use that as a guide alongside this calculator's estimate.
How much waste should I add for decking?
10% is a reasonable default for a simple rectangular deck laid straight. Diagonal patterns, picture-frame borders, or decks with lots of cuts around posts and stairs should use 15% or more.
Does this include joists, fasteners, or railing?
No — this calculator is for decking boards only. Joists, hardware, and railing are separate materials with their own quantities based on your framing plan.
Estimates only. Verify quantities with your supplier before purchasing.