Do Quick Calculation!

Perform fast calculations with our user-friendly online calculator! Conveniently crunch numbers and solve equations instantly. Ideal for quick math tasks, our tool simplifies your daily computations effortlessly. Try our intuitive calculator for accurate results on the go!

Composite Decking Calculator

Use our free Composite Decking Calculator to easily estimate how much composite decking you need by square feet, spacing, and dimensions. Plan your deck today with accurate results.

linear m/m²
This factor varies by brand. Default is 7.1 for Ecodek.
%
Typically 5-10%. For diagonal layouts, consider 15%.

Planning a new composite deck? Whether you're building a small backyard retreat or a spacious outdoor lounge, figuring out how much material you need is the first crucial step. That’s why we developed a Free Composite Decking Calculator to make this process fast, accurate, and stress-free.

With this online calculator, users can easily enter their deck dimensions and get instant results for decking boards, spacing, and total square footage. Our tool is optimized to give precise material estimates, helping DIYers and professionals alike save time and money. Plus, it works perfectly for estimating costs from top retailers like Home Depot and Lowe’s.

What is a Composite Decking Calculator?

A Composite Decking Calculator is a simple yet powerful tool that helps you estimate the total number of decking boards, joists, framing, and hidden fasteners required for your composite deck project. It considers your deck’s length and width, board size, and spacing to deliver accurate material and cost estimates.

Whether you’re using a decking calculator app or our online tool, it ensures you don’t overbuy or underbuy your decking materials.

How to Use the Composite Decking Calculator

Step-by-Step Instructions:

  1. Measure the deck area: Determine the length and width of the deck in feet (e.g., 20 feet by 20 feet).
  2. Select board size: Choose the width and length of the composite boards (e.g., 5.5 inches wide by 12 feet long).
  3. Set spacing: Typical spacing between boards is 1/8 inch (0.125 inches).
  4. Click Calculate: Instantly get the number of boards needed, total square footage, and optional framing and cost estimates.

Composite Decking Calculation Formula

Step 1: Calculate total square footage of your deck:

Deck Area (sq ft) = Length (ft) × Width (ft)

Example:

For a 20 x 20 deck:

Deck Area = 20 ft × 20 ft = 400 sq ft

Step 2: Calculate board coverage in square feet:

Each composite board covers:

Board Width (in) × Board Length (ft) ÷ 12 = Coverage in sq ft

For a 5.5 in wide by 12 ft long board:

5.5 × 12 ÷ 12 = 5.5 sq ft per board

Step 3: Estimate total number of boards:

Total Boards Needed = Total Deck Area ÷ Coverage per Board

400 ÷ 5.5 ≈ 73 boards

Note: Add 10% for cutting and waste:

73 × 1.10 ≈ 81 boards

Composite Deck Framing & Spacing Calculator

Framing and spacing are key to a strong, long-lasting deck. Here’s how to calculate:

Joist Spacing: Standard spacing is 16 inches on center.

Number of Joists:

Deck Width (in) ÷ Joist Spacing (in) + 1

Example for 12 ft deck width:

144 in ÷ 16 in + 1 = 10 joists

You’ll also need ledger boards, beams, and hardware depending on your layout.

How Much Does a Composite Deck Cost?

Composite decking costs vary based on brand, quality, and region. On average:

  • Price per board: $30–$60
  • Average installation: $20–$40 per sq ft (with labor)
  • DIY cost for 20x20 deck:
    - Material: 81 boards × $45 = $3,645
    - Optional framing/hardware: $1,000
    - Total Estimated Cost: $4,500–$6,000

Final Verdict

Using a composite decking calculator is the easiest way to plan your deck project accurately. It saves time, money, and eliminates the guesswork. Whether you’re shopping at Home Depot, Lowe’s, or using other brands, this calculator will help you buy exactly what you need and avoid unnecessary waste.

Our free deck board calculator with spacing is perfect for DIY homeowners, contractors, and architects. Don’t start your project without it!

Frequently Asked Questions (FAQs)

How do I calculate how much composite decking I need?

Measure your deck’s total area in square feet and divide it by the coverage area of one board. Don’t forget to add 10% for cuts and waste.

How many composite boards do I need for a 12x12 deck?

A 12x12 deck has 144 sq ft. With 5.5" x 12' boards, you’ll need approximately 30 boards (including 10% waste).

What is the downfall of composite decking?

Composite decking can be more expensive upfront, may get hot in direct sunlight, and may fade slightly over time.

Is this calculator suitable for all brands?

Yes! This calculator works for most composite decking brands including Trex, TimberTech, Fiberon, and others.