Common lengths: 8', 10', 12', 16', 20'
Standard: 10%, Angled cuts: 15%
Average: $10-$25 per sq ft (depending on material)
How to Calculate Decking
Area Calculation
Formula: Area = Length × Width
Example (16' × 20' deck):
- Area: 16 × 20 = 320 sq ft
- Boards (5.5" wide): ~70 boards with 10% waste
- Linear feet: ~1,120 ft
Board Sizes & Coverage
- 2×4 (3.5" actual): ~3.5" coverage width
- 2×6 (5.5" actual): ~5.5" coverage width (most common)
- Composite (6"): ~5.5" coverage width
- Wide Plank (12"): ~11.5" coverage width
Joist Spacing Guidelines
- 12" OC: Angled decking, high traffic
- 16" OC: Standard for most decking
- 24" OC: 2×6 or thicker boards only
Fastener Estimates
- Screws: 2 per joist per board
- Hidden Fasteners: 1.5-2 per joist per board
- Nails: Not recommended for decking
Cost Considerations
- Pressure Treated: $10-$15 per sq ft
- Cedar/Redwood: $18-$28 per sq ft
- Composite: $20-$35 per sq ft
- PVC/Vinyl: $25-$40 per sq ft
About This Calculator
Decking Calculator - Estimate Deck Materials & Cost
Calculate decking materials including boards, joists, and fasteners needed for your deck. Get accurate estimates for wood, composite, and PVC decking projects.
How to Use This Calculator
- Enter Deck Dimensions: Length and width in feet
- Select Board Size: Standard 2×6, 2×4, or composite sizes
- Set Joist Spacing: 12", 16", or 24" on center
- Board Length: Standard board length you'll use
- Get Results: Complete material list and cost
Decking Material Calculations
Area Formula
Formula:
Area = Length × Width (square feet)Boards Needed
Formula:
Boards per Row = Deck Width ÷ Board Width
Rows Needed = Deck Length ÷ Board Length
Total Boards = Boards per Row × Rows NeededBoard Sizes & Coverage
| Board Type | Nominal | Actual Width | Coverage |
|---|---|---|---|
| Standard 2×4 | 2" × 4" | 1.5" × 3.5" | 3.5" |
| Standard 2×6 | 2" × 6" | 1.5" × 5.5" | 5.5" |
| 5/4 × 6 | 1" × 6" | 1" × 5.5" | 5.5" |
| Composite | varies | ~5.5" | 5.5" |
| Wide Plank | 2" × 12" | 1.5" × 11.5" | 11.5" |
Joist Spacing Guidelines
| Spacing | Board Thickness | Best For |
|---|---|---|
| 12" OC | 5/4" or 2× | Angled decking, high traffic |
| 16" OC | 2× (most common) | Standard perpendicular installation |
| 24" OC | 2×6 only | Economy, heavy boards |
Fastener Requirements
- Deck Screws: 2 screws per joist per board
- Hidden Fasteners: 1.5-2 per joist per board
- Example: 16' joists with 16" spacing = ~300-400 screws per 100 sq ft
Material Cost Per Square Foot
| Material | Material Only | Installed |
|---|---|---|
| Pressure Treated | $10-$15/sq ft | $20-$35/sq ft |
| Cedar | $15-$20/sq ft | $30-$45/sq ft |
| Redwood | $18-$25/sq ft | $35-$55/sq ft |
| Composite | $15-$25/sq ft | $30-$50/sq ft |
| PVC | $20-$30/sq ft | $40-$60/sq ft |
Waste Factor Guidelines
| Installation | Waste Factor |
|---|---|
| Standard perpendicular | 10% |
| Angled/diagonal (45°) | 15% |
| Herringbone/pattern | 20-25% |
| Complex curves | 25%+ |
Additional Materials Needed
- Joists: Typically 2×8 pressure-treated lumber
- Beams: 2×10 or 2×12 for structural support
- Posts: 4×4 or 6×6 for support
- Concrete: For footings (check local codes)
- Flashing: Ledger board flashing
- Railings: Required for decks 30" or higher
Installation Tips
- Use only rated fasteners for pressure-treated lumber
- Leave 1/8" gap between boards for drainage
- Install joist tape for longer deck life
- Pre-drill boards near ends to prevent splitting
- Use hidden fasteners for a clean look
- Consider board orientation for sun exposure
Common Deck Sizes
| Size | Area | Typical Use |
|---|---|---|
| 12' × 12' | 144 sq ft | Small patio replacement |
| 12' × 16' | 192 sq ft | Small dining/decking |
| 14' × 20' | 280 sq ft | Medium dining/decking |
| 16' × 20' | 320 sq ft | Large entertaining area |
| 20' × 20' | 400 sq ft | Multi-use space |
Frequently Asked Questions
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