Decking Board Calculator
Buying decking? Enter your deck size and board dimensions to get the number of boards and total linear feet — with a 10% waste allowance built in.
Decking Board Calculator
Why use the Decking Board Calculator
Guess board counts and you either fall short or overspend. This counts them, waste included.
How to get your numbers
- Deck length & width.
- Board width, length and the gap between boards.
- Add extra for diagonal or picture-frame patterns.
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How to use it
- Enter your deck length and width.
- Enter your board width, length and the gap between boards.
- Order the 10%-waste figure, more for diagonal patterns.
Frequently asked questions
How many deck boards do I need?
Divide the deck area by each board’s coverage (board width plus gap × board length), then add about 10% for waste and cuts.
What gap should I leave between deck boards?
About ⅛ inch for composite and dry lumber; wet pressure-treated boards shrink as they dry, so they can be butted tighter.
Why should I buy extra deck boards?
Cuts, defects and pattern layouts create waste. A 10% cushion (more for diagonal decking) keeps you from a second trip to the yard.
What is the difference between linear feet and board count?
Linear feet is the total running length of decking you need; board count divides that by each board’s length to get the number to buy.
How wide are standard deck boards?
Most are 5½ inches wide (nominal 6-inch); some composites and specialty boards run narrower. Enter your actual width for an accurate count.
Do diagonal decking patterns need more boards?
Yes — angled and picture-frame layouts create more offcuts, so add roughly 15% instead of 10% for waste.
How do I calculate deck square footage?
Multiply the deck length by its width. For L-shapes, split into rectangles, calculate each, and add them together.
