Deck board calculator
Enter the deck size, the board you are actually buying and the length your yard sells, and this gives you the row count, the board count with waste, the screws and the material cost. It uses the board's real face width — nominal 6-inch stock lays 5.5", not six.
Prices move weekly and by region. Enter the unit price your yard quoted you — the defaults are round placeholders, not a market average.
What it counts
Rows are the deck's width divided by the board's face width plus the gap. Boards are rows multiplied by how many stock lengths it takes to cross the deck, then increased by your waste factor. Screws assume two per board at every joist crossing.
It does not add a picture-frame border, fascia, or the extra boards a diagonal layout eats. Add those as separate lines — a 45-degree layout typically wants a noticeably higher waste factor because every board is cut twice.
Worked example
A 12 × 16 deck in 5/4×6 at a quarter-inch gap: the 12-foot width takes 26 rows. Buying 16-foot boards, each row is one board, so it is that many boards plus waste — and buying 8-foot stock instead doubles the board count and puts a butt joint in every single row, which is exactly the layout to avoid.
| Deck width | Rows at 5/4×6 |
|---|---|
| 8 ft | 17 |
| 10 ft | 21 |
| 12 ft | 26 |
| 14 ft | 30 |
| 16 ft | 34 |
Waste factor
Ten percent covers a simple rectangle in straight rows. Push it higher for a diagonal layout, for a deck with several angles, or when you are buying a length that does not divide neatly into your deck — the offcut from every row is the waste.
The cheapest way to cut waste is to buy lengths that match the deck, which is a decision you make with the joint plan in front of you, not at the till.
Sources
Nothing here is asserted as a current figure. The tool is arithmetic on what you type, and every default is a round placeholder for your yard's quote.
Next on the pile
Board spacing calculator
Gap, count and where the butt joints land.
Decking board width
Why the face width is not the nominal one.
How to stagger deck boards
Plan the joints before you buy lengths.
Deck cost calculator
The whole deck, not just the surface.
Deck joist span calculator
Size the frame these boards sit on.