Precise board counts, lumber efficiency, and cost estimates for any deck layout.
Project Specs
Deck Dimensions
Blueprint View
Live Preview
12' × 10'
Precision Settings
Project Summary
Total Estimated Cost$0.00$0.00/sq ft
Price Per Board ($)
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Bill of Materials
Lumber Efficiency
Item
Qty
Notes
Deck Boards
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Screws
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Screw Boxes
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Total Area
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Board Count
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Linear Feet
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Efficiency
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Screw Count
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Total Cost
Boards= LF ÷ Board Length =--
Screws= Area × Joist Factor =--
Cost= Boards × Price + Fasteners =--
📐Diagonal pattern: 15% extra material included for angled cuts at the deck perimeter.
⚠️Composite decking requires 12" OC joist spacing to prevent sagging. Switch your joist spacing above.
🖼️Picture frame border included in board count. The border boards run around the full perimeter.
🏗️Large deck (>500 sq ft): Consider ordering boards in bulk for delivery pricing and check local permit requirements.
💡Low lumber efficiency: Try a longer board length to reduce off-cuts and save money.
Deck Boards
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Fasteners
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Total Cost
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Cost Per Sq Ft
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Cost Breakdown
Material Comparison — Your Deck Size
Material
Price/Board
Total Cost
Cost/Sq Ft
Lifespan
Maintenance
Switch to this tab after calculating to see comparisons.
💾 Saved Projects
🛒 Materials Checklist
Run the calculator first to generate your list.
⏱ Project Timeline Estimate
Calculate first to see timeline.
📋 Permit & Code Notes
Most jurisdictions require a building permit for decks over 30 inches above grade or larger than 200 sq ft.
Common code requirements include: minimum footing depth (below frost line), maximum joist span tables, railing height (36–42 inches), and baluster spacing (<4 inches).
Always check with your local building department before starting construction. Permit fees typically range $150–$600.
How to Use This Calculator
1
Measure the deck footprint
Enter the length and width of your deck surface in feet. All calculations update instantly as you type. For irregular shapes, calculate as a rectangle and subtract any cutouts.
2
Choose decking material
Select pressure-treated lumber, composite, cedar, or redwood. Each material has a different price per board and maintenance requirement. Composite costs more upfront but requires no staining or sealing.
3
Set board width and spacing
Select standard board width (5/4×6 is most common) and gap size. The standard gap is 1/8 inch for pressure-treated and 3/16 inch for composite to allow expansion and drainage.
4
Pick fastener pattern
Choose standard perpendicular, diagonal (adds 15% waste), or picture frame border. Select hidden fasteners if using a clip system for a clean, fastener-free surface appearance.
5
Get board count and material list
Read total board count, linear feet, screw quantity, joist count, and estimated material cost. Switch to the Materials tab for a full cost breakdown by component.
Screws per board2 fasteners × joist count per board
Key Terms
Decking Board — The horizontal surface boards that form the walking surface of the deck. Most common: 5/4×6 (1" thick × 5.5" wide) or 2×6. Length: 8, 12, 16, or 20 feet.
Joist — A horizontal structural member that supports the decking boards. Typically pressure-treated 2×8 or 2×10 lumber, spaced 12 or 16 inches on center. Joists rest on beams or the ledger board.
Ledger Board — A pressure-treated board bolted to the house rim joist that supports one end of the deck frame. Must be properly flashed to prevent water from penetrating the house structure.
Fascia — A finishing board installed vertically around the deck perimeter, covering the cut ends of decking boards and the rim joists for a clean, finished appearance.
Hidden Fastener — A clip system that secures decking boards from the side, leaving a fastener-free walking surface. Required for many composite decking brands. Adds 15–20% to fastener cost but improves appearance significantly.
Composite vs Pressure-Treated — Composite boards (wood fiber + plastic) resist rot, splinters, and fading; require no staining; last 25–30 years. Pressure-treated lumber costs 3–5× less but requires annual or biennial sealing and may warp or splinter over time.
Frequently Asked Questions
What gap should I leave between deck boards?
For pressure-treated lumber: 1/8 inch (the width of a 16d nail) allows drainage and expansion while preventing debris buildup. For composite boards: 3/16 inch as most manufacturers specify, since composite expands more with heat than wood. Using a spacer tool ensures consistent gaps. Never install composite boards touching — thermal expansion can cause buckling.
How long does composite decking last compared to wood?
Quality composite decking (Trex, TimberTech, Fiberon) carries 25–30 year warranties and typically lasts that long with minimal maintenance — just an annual cleaning. Pressure-treated pine lasts 15–25 years with proper sealing every 1–2 years. Cedar and redwood last 20–30 years with regular maintenance. Composite has higher upfront cost but lower lifetime cost due to zero maintenance spending.
What joist spacing do I need?
For 5/4×6 decking boards: 16 inches on center maximum. For 2×6 lumber or composite boards running perpendicular: 16 inches OC. For diagonal deck boards: 12 inches OC maximum (boards span farther between supports on a diagonal). For composite boards running at an angle: check manufacturer specs — most require 12 inches OC or closer.
Do I need to seal or stain pressure-treated decking?
New pressure-treated lumber should be allowed to dry for 3–6 months before sealing — fresh PT lumber won't absorb finish well. After drying, apply a water-repellent sealer or semi-transparent stain every 1–2 years to prevent cracking, checking (surface splits), and UV graying. Use products rated for pressure-treated lumber. Unfinished PT will gray and crack more quickly but will not rot — the preservative treatment handles rot.
How to Use This Calculator
1
Enter Deck Dimensions
Input the length and width of your deck surface in feet. All results update instantly as you type.
2
Select Board & Material
Choose your board width, material type, and board length. Price per board auto-fills based on your selection and typical market rates.
3
Review & Save
See boards, screws, efficiency, and total cost in real time. Switch to Materials tab for cost breakdown or Planner tab to save and generate a shopping list.
A horizontal structural member that supports the deck boards, typically pressure-treated lumber spaced 12–16 inches on center.
Ledger Board
A horizontal board bolted to the house framing that supports one end of the deck. Proper flashing over the ledger prevents water intrusion into the structure.
Post Footing
A concrete pier that supports the vertical posts holding up the deck frame. Sized per local frost depth and load requirements.
Pressure-Treated Lumber
Wood infused with preservatives to resist rot, insects, and fungal decay. Required for all ground-contact and structural components.
Picture Frame Border
A single row of boards running around the deck perimeter, perpendicular to the inner boards. Hides cut end-grain and creates a finished, professional edge.
Lumber Efficiency
The percentage of purchased board length that is actually used. Higher efficiency means less off-cut waste and lower total cost.
Real-World Examples
Example 1
Standard Backyard Deck — Pressure Treated
16ft × 12ft deck, 5/4×6 boards at 12ft length, 1/8" gap, 16" OC, standard layout with picture frame, $15/board
Result: ~54 boards, ~1,152 screws (4 boxes), lumber efficiency ~88%, estimated total cost ~$900. Ideal entry-level deck with full structural flexibility.
Result: ~68 boards (15% diagonal waste), ~2,270 screws, estimated total ~$4,200. Low maintenance investment — no staining, 25–30 year lifespan.
Decking Material Comparison
Material
Cost / Sq Ft
Lifespan
Maintenance
Best For
Pressure-Treated Pine
$2–$5
10–15 years
Stain every 2–3 years
Budget builds
Cedar / Redwood
$4–$8
15–25 years
Seal every 1–2 years
Natural look
Composite (mid-range)
$6–$12
25–30 years
Wash annually
Low maintenance
PVC / Capped Composite
$8–$15
30+ years
Minimal
Coastal / wet climates
Ipe Hardwood
$8–$15
40+ years
Oil annually or let silver
Premium aesthetics
Planning Your Deck Build
Permits and Code Requirements
Most jurisdictions require a building permit for decks over 30 inches above grade or larger than 200 sq ft. Common code requirements include minimum footing depth (below frost line), maximum joist span, railing height (36–42 inches), and baluster spacing (less than 4 inches). Check with your local building department before starting. Failing to permit can create title issues when you sell your home.
Wood vs. Composite: The 20-Year Math
Pressure-treated wood costs roughly half as much upfront but requires sanding, staining, and sealing every 2–3 years. Over 20 years, maintenance costs for a 300 sq ft deck can exceed $3,000 — often more than the original material cost. Composite decking eliminates most maintenance, and modern products closely mimic natural wood grain. For decks you plan to keep long-term, composite often has the better total cost of ownership.
Maximizing Lumber Efficiency
The key to minimizing waste is choosing a board length that divides evenly into your deck length. For a 12ft deck, 12ft boards achieve near-100% efficiency. For a 16ft deck, 8ft or 16ft boards work perfectly. The calculator's efficiency bar shows exactly how well your current board length is performing — try switching between lengths to find the optimal choice.
Frequently Asked Questions
How do I calculate how many deck boards I need?
Calculate your total square footage (Length × Width), then determine how many linear feet of board are needed to cover that area given the board width and gap. Divide by board length and add your waste factor — 10% for standard layouts, 15% for diagonal.
What joist spacing should I use for composite decking?
Composite decking requires 12" on-center joist spacing. Unlike solid wood, composite boards are hollow or semi-hollow and can sag over longer spans, especially in hot weather. Most manufacturer warranties are void if installed at 16" OC. The calculator will alert you if your current joist spacing is insufficient for composite.
How much gap should I leave between deck boards?
A gap of 1/8" to 1/4" is standard. Wood boards expand and contract with moisture changes — too little gap and boards will buckle; too much and debris accumulates. Composite boards expand less but still need a 3/16" gap per manufacturer specs.
Why does diagonal decking use more material?
Installing boards at 45° creates triangular waste triangles at all four corners and along the perimeter edges. The calculator correctly applies a 15% waste factor for diagonal layouts (vs 10% for standard), which is the industry-standard recommendation.
What is a picture frame border?
A picture frame border is a single row of boards running around the perimeter of the deck, perpendicular to the inner field boards. It hides the cut end-grain of the inner boards, creates a clean professional edge, and adds visual interest. The calculator includes the border boards in the total board count.
Is composite decking worth the higher cost?
For most homeowners planning to keep their deck 10+ years, yes. While composite costs 2–3× more upfront, you save on annual staining and sealing (typically $300–$600 for a 300 sq ft deck), and the 25–30 year lifespan often exceeds pressure-treated wood at lower long-term total cost.
How do I choose the right board length?
Choose a board length that divides evenly into your deck length. For a 12ft deck, use 12ft boards (100% efficiency). For a 14ft deck, 14ft boards may not be available — try 16ft boards and use the offcuts elsewhere. The calculator's Lumber Efficiency bar shows which board length gives the least waste for your specific dimensions.
Do I need a permit to build a deck?
Most jurisdictions require a permit for decks over 30 inches above grade, attached to the house, or larger than 200 sq ft. Requirements vary by location — always check with your local building department before starting. Unpermitted decks can create problems when selling your home and may not comply with safety codes.