Deck Board Calculator
Decking boards and screws from deck size and board dimensions.
1/8 to 1/4 in. Wet pressure-treated boards shrink, so they are often laid tight.
You need
29 boards
Waste included. Cull twisted boards at the yard; they do not straighten.
- Board rows
- 26 rows
- Deck area
- 192 sq ft
- Deck screws
- 675 screws
Estimates only. Verify quantities before ordering.
How this is calculated
Rows = deck width in inches / (board width + gap), rounded up. Boards per row = deck length / board length, rounded up. Total = rows x boards per row plus waste. Screws assume about 3.5 per square foot (two per board at each 16 in joist).
Enter the deck dimensions, pick your board size and gap, and this calculator counts the boards and screws. It works row by row: how many board widths (plus gaps) span the deck, times how many board lengths cover each row, plus waste for cuts and culls.
Buy boards as long as your deck allows. A 16 ft deck covered with 16 ft boards has no butt joints, which look better and last longer than seams. Where joints are unavoidable, they must land on a joist, stagger between rows, and that cutting is why the waste factor defaults to 10%.
Boards for common deck sizes
Rows assume 5.5 in boards, a 1/4 in gap, 16 ft stock, and 10% waste.
| Deck size | Boards | Screws |
|---|---|---|
| 10 x 10 ft | 24 boards | 350 screws |
| 12 x 12 ft | 29 boards | 500 screws |
| 16 x 12 ft | 29 boards | 675 screws |
| 20 x 14 ft | 66 boards | 975 screws |
| 24 x 16 ft | 75 boards | 1,350 screws |
Pressure treated, cedar, or composite
Pressure treated pine is the cheapest and the most common, and modern treatments are copper based rather than the arsenic compounds used before 2004. It is structurally sound and takes stain well once it has dried out, which can take several months on a new deck. It also moves a lot as it dries, cupping and checking, so boards need fastening in a way that accommodates that.
Western red cedar and redwood are naturally rot resistant, lighter, more dimensionally stable, and considerably more expensive. They weather to a silver gray if left alone or need refinishing every couple of years to hold their color. Their softness is the trade-off: cedar dents under furniture and heavy traffic more readily than treated pine.
Composite and PVC decking cost the most up front and remove nearly all the maintenance. They do not rot, split, or need staining, and most carry long warranties. They do get hot in direct sun, particularly in dark colors, they sag more than wood over the same joist spacing, and scratches cannot be sanded out the way they can in a wood deck. Check the required joist spacing before framing, since many composites need 12 or 16 inches on center where wood would have allowed more.
Board width, spacing, and the direction you run them
Nominal 5/4 by 6 decking is the usual choice and actually measures about 5 and a half inches wide, which is the figure the count above uses. Nominal 2x6 boards are thicker and stiffer for the same width, useful over wider joist spacing or where the deck carries heavy loads. Narrower 4 inch boards look finer and cost more per square foot of coverage because you need more of them and more fasteners.
Leave a gap between boards for drainage and airflow. Wet treated lumber installed tight will shrink and open its own gaps, sometimes to a quarter inch or more, so those boards go down nearly touching. Dry material and composites are installed with a deliberate gap, typically an eighth of an inch, using a spacer. Getting this backwards produces either a deck with gaps wide enough to lose things through or one with no drainage at all.
Running boards diagonally at 45 degrees adds roughly 15 percent to the material because of the angled cuts at every edge, and it requires joist spacing to be tightened since the effective span across a diagonal is longer. It stiffens the frame and looks deliberate, but budget for both the extra boards and the extra framing.
Fastening: face screws or hidden clips
Face screwing with two coated deck screws per joist is the traditional method: fast, cheap, strong, and the fastener heads are visible. Use screws rated for the treatment chemicals in modern lumber, since ordinary steel corrodes quickly in contact with copper-based preservatives. Predrilling near board ends prevents splitting, which matters most on the last few inches of every board.
Hidden fastener systems clip into a groove on the board edge and leave a clean surface with no visible heads. They cost more, take longer, and set the board spacing for you. Most grooved composite decking is designed around them. The practical downside is repairability: pulling a single damaged board from the middle of a clipped deck is considerably more work than backing out four screws.
Whichever you use, stagger the butt joints between boards so they do not line up across the deck, and make sure every butt joint lands on a joist with enough bearing for both boards. Doubling the joist at planned joint locations is worth doing during framing and impossible to add later.
Common questions
How many deck boards do I need per square foot?
With standard 5.5 inch boards and a 1/4 inch gap, each linear foot of board covers about 0.48 square feet, so plan on roughly 2.1 linear feet of decking per square foot of deck, plus waste. A 200 square foot deck is about 420 linear feet of boards.
What gap should I leave between deck boards?
Aim for 1/8 to 1/4 inch in service. Kiln-dried and composite boards are installed at that gap. Wet pressure-treated lumber is usually laid tight because it shrinks about 1/4 inch as it dries, opening its own gap. Check the moisture of your boards before choosing.
Screws or hidden fasteners?
Face screws are cheapest, strongest, and easy to service: use coated or stainless deck screws, two per board at every joist. Hidden clip systems give a cleaner surface on grooved composite boards at extra cost. Never use uncoated screws or nails on treated lumber; the chemicals corrode them.
Which way should deck boards run?
Perpendicular to the joists, always. Beyond that, boards running parallel to the house's long dimension usually look best and shed water along their length. If the deck is longer than your boards in one direction, run boards the other way to avoid butt joints entirely.