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Decking Calculator

Calculate deck board count, joist spacing, fastener quantities, and material costs for your deck project. Compare pressure treated, cedar, composite, PVC, and Ipe decking prices instantly.

100% Free5 Material TypesInstant Results
Deck Dimensions
16 ft
8 ft50 ft
12 ft
8 ft30 ft
Deck Area: 192 sqft
Board Width
Board Length
Decking Material
Railing
Auto: 44 ft (3 open sides)

Default assumes one side against the house. Override if needed.

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How It Works

Get a complete deck material estimate in three simple steps.

Enter Deck Size

Use the sliders to set your deck length and width in feet. Pick your board width and length to match what is available at your local supplier.

Choose Your Material

Select from five popular decking materials: pressure treated pine, cedar, composite (Trex/TimberTech), PVC vinyl, or Ipe hardwood.

Get Your Estimate

Instantly see board count, joists, fasteners, railing costs, and a full material price comparison so you can shop with confidence.

Decking Material Cost Comparison (2026)

Average material-only cost per square foot for the most popular deck board options. Use these ranges with our deck price calculator for a complete project estimate.

MaterialLow ($/sqft)High ($/sqft)
Pressure Treated Pine$2$5
Cedar$4$8
Composite (Trex/TimberTech)$6$12
PVC / Vinyl$8$14
Ipe / Hardwood$8$15

Prices reflect material cost only. Professional installation adds $8–$22 per square foot depending on region and deck complexity. Composite decking prices from brands like Trex and TimberTech may vary by product line.

Deck Joist Spacing Reference

Proper joist spacing is critical for a safe, code-compliant deck. The deck joist spacing calculator above uses 16-inch on-center spacing as the standard. Here is a quick reference for common scenarios.

Board DirectionPerpendicularDiagonal (45°)
Pressure Treated (5/4")16" o.c.12" o.c.
Cedar (5/4")16" o.c.12" o.c.
Composite (standard)16" o.c.12" o.c.
Composite (capped)16" o.c.12" o.c.
PVC / Vinyl16" o.c.12" o.c.
Ipe Hardwood16"–24" o.c.16" o.c.

Always follow the decking manufacturer's installation guide and local building codes. The deck beam span calculator and joist span tables in the IRC (International Residential Code) provide structural requirements.

Deck Board Layout Tips

A well-planned board layout reduces waste, minimizes cuts, and gives your deck a polished look. Here are the most important deck board spacing and layout best practices.

Stagger End Joints

Offset butt joints by at least 2 joist bays (32 inches minimum) between adjacent rows. This prevents a visible line of joints running across the deck and improves structural integrity.

Maintain Consistent Gaps

Use a 1/8-inch gap between deck boards for drainage and expansion. A 16d nail or a dedicated spacer tool works perfectly. Composite boards may require wider gaps per manufacturer specifications.

Crown Side Up

For natural wood decking, install boards with the bark side (crown) facing up. This encourages water to run off rather than pooling in the concave surface as the board dries and cups.

Start From the House

Begin laying boards from the house side outward. This way, the first row is tight against the ledger board, and any partial-width rip cut ends up at the outer edge where it is less noticeable.

Plan for Stair Transitions

When your deck includes stairs, plan the board layout so a full-width board lands at the stair header. Use the deck step calculator to determine stair riser count and tread depth before finalizing the framing.

Account for Overhangs

Allow boards to overhang the outer joist by 1 to 1.5 inches. This creates a clean edge, hides the rim joist, and channels water drip away from the substructure.

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Frequently Asked Questions

Common questions about deck sizing, materials, and costs answered.

For a 12x16 ft deck (192 sqft) using standard 5.5-inch wide by 12-ft long boards, you need approximately 42-46 boards including a 10% waste allowance. The exact count depends on your board width, board length, and layout pattern. Use the deck board calculator above for a precise number based on your specific dimensions and materials.
Multiply your deck length by its width in feet to get the square footage. For example, a 16 ft x 12 ft deck equals 192 square feet. For L-shaped or irregular decks, break the shape into rectangles, calculate each one separately, and add them together. Our deck square footage calculator does this math instantly.
Pressure treated pine offers the lowest upfront cost at $2-$5 per square foot, but composite decking (like Trex or TimberTech) at $6-$12 per square foot often provides better long-term value. Composite requires no staining, sealing, or annual maintenance, and typically lasts 25-50 years compared to 10-15 years for treated lumber. Over a 25-year span, composite decking usually costs less when you factor in maintenance expenses.
Plan for approximately 350 screws per 100 square feet of decking, or about 3.5 screws per square foot. This accounts for standard 16-inch joist spacing with two screws per board at each joist crossing. For composite and PVC decking using hidden fasteners, you need roughly 90 clips per 50 square feet. The deck board calculator above automatically calculates the right fastener count for your material type.
The standard deck joist spacing is 16 inches on-center for most decking materials, including pressure treated lumber, cedar, and standard composite boards. Some composite and PVC manufacturers allow 12-inch spacing for diagonal installations or stair treads. Always check your decking manufacturer's installation guide for specific joist spacing requirements.
A 20x20 ft deck (400 sqft) costs between $800-$2,000 for pressure treated pine materials, $2,400-$4,800 for composite, or $3,200-$6,000 for PVC decking -- these are material-only costs. Add roughly $15-$35 per square foot for professional labor. Total installed cost for a 20x20 deck typically ranges from $7,000 (basic pressure treated) to $20,000+ (premium composite with railing). Use our deck price calculator for your exact dimensions.
Add a 10% waste allowance for standard rectangular decks with boards running straight. Increase to 15% for diagonal board patterns, and up to 20% for complex deck shapes with many angles, curves, or built-in features like benches. Our lumber calculator for deck projects includes 10% waste by default to ensure you order enough material.
The most common deck board width is 5.5 inches (nominal 6 inches), which provides a traditional look and spans standard 16-inch joist spacing well. Narrow 3.5-inch boards (nominal 4 inches) create a more refined appearance and are popular for smaller decks and porch floors. Longer boards (16 ft or 20 ft) reduce the number of butt joints but may be harder to find and transport. For board length, 12 ft and 16 ft are the most widely available and cost-effective options.
Measure the total linear footage of railing needed -- typically the perimeter minus the side attached to your house. Railing costs range from $20-$35 per linear foot for pressure treated wood, $30-$55 for composite, and $35-$60 for PVC or aluminum systems. A 16x12 ft deck with three open sides needs about 44 linear feet of railing, costing $880-$2,640 depending on material. Our calculator includes railing estimates automatically.
Composite decking is worth it for most homeowners when you consider the full cost of ownership. While initial material cost is 2-3x higher than pressure treated wood, you save $500-$1,000+ in maintenance over 10 years (no staining, sealing, or board replacement). Composite decks also maintain consistent appearance, resist rot and insects, and typically increase home resale value more than wood decks. The break-even point is usually 7-10 years of ownership.

Planning a bigger outdoor project?

Use our Aggregate Calculator to estimate gravel, crushed stone, and base material quantities for your deck footings and landscaping.

Aggregate Calculator

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