Calculate the number of deck boards, screws, and total material cost for any deck project. Supports wood, composite, and PVC materials.
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320 sq ft deck, 16-ft boards
| Deck Area | 320 sq ft |
|---|---|
| Board Rows | 43 |
| Total Boards | 48 |
| Total Linear Feet | 768 |
| Board Cost | $2,464.00 |
| Screws Needed | 1,152 |
| Screw Boxes (350ct) | 4 |
| Screw Cost | $220.00 |
| Total Material Cost | $2,684.00 |
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Pressure-treated (PT) lumber remains the most affordable decking option at $2 to $4 per square foot for materials. Southern yellow pine treated with micronized copper azole (MCA) or alkaline copper quaternary (ACQ) is the standard product. PT decking is strong, readily available, and easy to work with using standard tools. A 320-square-foot deck costs $640 to $1,280 in PT boards alone.
The downside is maintenance. PT wood must be sealed or stained every 1 to 2 years to prevent graying, splitting, and moisture damage. Stain and sealer cost $0.75 to $1.50 per square foot per application, adding $240 to $480 annually. Over 25 years, maintenance costs $6,000 to $12,000, potentially exceeding the initial savings over composite. PT decking typically lasts 15 to 25 years before boards need replacement, though the substructure often lasts longer.
Composite decking has evolved dramatically since its introduction. Modern capped composites use a wood-plastic core wrapped in a protective polymer shell that resists fading, staining, scratching, and moisture. Budget composites (Trex Enhance, Fiberon Good Life) run $4 to $6 per square foot. Mid-range options (Trex Select, TimberTech PRO) cost $6 to $8 per square foot. Premium lines (Trex Transcend, TimberTech AZEK Vintage) command $8 to $11 per square foot.
The maintenance advantage is significant. Composite decking requires only periodic cleaning with soap and water. No staining, sealing, or sanding is needed. Over 25 years, maintenance costs are $500 to $1,000 total (cleaning supplies and occasional pressure washing), compared to $6,000 to $12,000 for wood. When combined with the longer 25 to 50-year lifespan, mid-range composite offers the best total cost of ownership for most homeowners. The material feels different underfoot than wood, which some homeowners prefer and others do not.
Western red cedar decking costs $5 to $8 per square foot and offers natural beauty and rot resistance without chemical treatment. Cedar is lighter than PT pine, naturally repels insects, and ages to an attractive silver-gray if left untreated. However, cedar is softer than PT wood and more susceptible to surface damage from furniture and foot traffic. Regular oiling ($0.50 to $1.00 per square foot annually) maintains the original color.
Tropical hardwoods like ipe, cumaru, and tigerwood cost $8 to $15 per square foot but offer exceptional durability with 40 to 75-year lifespans. Ipe is nearly as hard as concrete, naturally fire-resistant, and impervious to insects and rot. The main drawbacks are high cost, difficulty working with (requires pre-drilling and carbide-tipped blades), and environmental concerns about tropical hardwood sourcing. FSC-certified options are available at a 10 to 20 percent premium.
PVC (polyvinyl chloride) decking contains no wood fiber, making it completely moisture-proof. Brands like AZEK and Wolf PVC run $9 to $12 per square foot. PVC decking does not fade, stain, rot, or support mold growth. It stays cooler underfoot than composite in direct sunlight and is the lightest decking material available. PVC is the best choice for pool surrounds, waterfront properties, and coastal environments where salt spray is a concern. The main disadvantage beyond cost is thermal expansion: PVC boards expand and contract more than composite, requiring careful attention to manufacturer-specified gapping.
The fundamental calculation divides the deck length (the dimension parallel to the boards) by the board coverage width. A standard 5.5-inch deck board with a 3/16-inch gap covers 5.6875 inches or approximately 0.474 feet per board. For a 20-foot deck dimension, you need 20 divided by 0.474, which equals approximately 42 rows of boards.
Next, determine how many boards are needed per row. If your deck width is 16 feet and you are using 16-foot boards, each row requires one board. If using 12-foot boards, you need two boards per row with a butt joint (always on a joist). For the 42-row, 16-foot-wide deck example, using 16-foot boards means 42 boards; using 12-foot boards means 84 boards. Joints should be staggered so adjacent rows do not joint at the same location.
The board pattern dramatically affects waste. A straight perpendicular layout with boards matching the deck width generates only 5 to 8 percent waste from defective boards and minor trimming. A perpendicular layout requiring butt joints generates 8 to 12 percent waste due to trimming boards to land on joists. Diagonal patterns generate 15 to 20 percent waste because every board at the deck edges must be angle-cut. Picture frame borders (a perimeter board running perpendicular to the field boards) add approximately 5 percent more material for the border.
Herringbone and chevron patterns generate the highest waste at 20 to 25 percent, as every board requires angled cuts. These complex patterns also significantly increase installation labor. For most residential decks, a simple perpendicular layout with a picture frame border provides an attractive look with manageable waste. If budget allows for premium appearance, a diagonal pattern at 45 degrees adds visual interest with a modest waste increase.
Hidden fastener systems are increasingly popular for composite decking, providing a clean top surface without visible screws. Systems like Trex Hideaway, CAMO Edge, and Tiger Claw clip-type fasteners cost $80 to $120 per 100 square feet of coverage. Face screwing with composite-specific screws costs $45 to $65 per 100 square feet. Each face-screwed board needs 2 screws per joist. At 16-inch joist spacing, a 16-foot board crosses 13 joists, requiring 26 screws per board.
For a 320-square-foot deck, plan on 1,000 to 1,400 face screws or 80 to 100 hidden fastener clips plus 100 to 150 starter and finish screws. Always use manufacturer-approved fasteners for composite decking, as using the wrong screw type can void the warranty. Stainless steel screws are required for most composite products and for all PT wood decking treated with ACQ or MCA preservatives, as these treatments corrode standard galvanized fasteners.
Divide the deck length by the board width plus gap. For 5.5-inch boards with 1/8-inch gap, each board covers 5.625 inches. A 20-foot deck length needs approximately 43 boards. Add 10 to 15 percent for waste, especially for diagonal or picture-frame patterns.
In 2026, composite decking material costs $4 to $11 per square foot depending on brand and quality. Budget composites run $4 to $6, mid-range $6 to $8, and premium (capped polymer) $8 to $11. Pressure-treated wood runs $2 to $4 per square foot for comparison.
The most common deck board width is 5.5 inches (nominal 6-inch or actual 5.5-inch for wood, similar for composites). Some composite brands offer wider boards at 7.25 inches. Wider boards reduce the number of boards needed but may be more prone to cupping.
For wood decking, leave 1/8 inch between boards when installed dry (wood will shrink as it dries). For composite decking, follow the manufacturer gap specification, typically 3/16 to 1/4 inch for thermal expansion. End-to-end gaps between board ends should be 1/8 to 3/16 inch.
Quality composite decking lasts 25 to 50 years with minimal maintenance. Capped composites with polymer shells are the most durable, resisting fading, staining, and scratching. Budget composites may show wear after 15 to 20 years. Most premium brands offer 25-year fade and stain warranties.
Deck boards typically run perpendicular to the house (and parallel to the joists beneath). This is structurally efficient, minimizes waste, and provides proper drainage away from the house. Diagonal patterns add visual interest but increase waste by 15 to 20 percent.
Use 2 screws per joist connection (one near each edge). For 16-inch joist spacing on a 12-foot-long board, you need approximately 18 screws per board (9 joist connections x 2 screws). A 320-square-foot deck needs roughly 1,000 to 1,200 screws.
It is not recommended. Installing new boards over old creates moisture traps, adds excessive weight, and makes it impossible to inspect the substructure. Remove old decking, inspect and repair joists and ledger, then install new boards on the existing frame.
Boards = (Deck Length / Board Width+Gap) x Rows
Rows = Deck Width / Board Length (rounded up)
Add waste factor for pattern and cuts
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