Composite Decking Calculator
12 feet
16 feet
20 feet
3.5 inches (Nominal 4″)
5.5 inches (Nominal 6″)
7.25 inches (Nominal 8″)
Understanding Composite Decking Calculations
Planning a new deck or renovating an existing one with composite materials? Our Composite Decking Calculator helps you accurately estimate the number of boards you'll need, saving you time and preventing costly over-purchasing or frustrating shortages.
What is Composite Decking?
Composite decking is a popular alternative to traditional wood, made from a blend of recycled plastic and wood fibers. It offers durability, low maintenance, and resistance to rot, insects, and fading, making it an excellent choice for outdoor living spaces.
How to Measure Your Deck Area
To use the calculator effectively, you'll need the basic dimensions of your deck:
- Deck Length: Measure the longest side of your deck in feet.
- Deck Width: Measure the shorter side of your deck in feet.
For irregularly shaped decks, it's best to break the area down into simple rectangles, calculate each section, and then sum them up. For this calculator, assume a rectangular or square deck.
Understanding Board Dimensions
Composite decking boards come in various standard lengths and widths:
- Board Length: Common lengths are 12, 16, and 20 feet. Choosing the right length can minimize waste, especially if your deck dimensions are close to these standard sizes.
- Board Width: While often referred to by nominal sizes (e.g., "6-inch board"), the actual width is usually slightly less (e.g., 5.5 inches). Our calculator uses actual board widths for precision.
The Importance of a Waste Factor
When ordering building materials, it's crucial to account for a "waste factor." This percentage covers:
- Cuts: Boards will need to be cut to fit the exact dimensions of your deck, around posts, or for angled sections.
- Mistakes: Even experienced DIYers can make miscuts.
- Damage: Occasionally, a board might arrive slightly damaged or get damaged during installation.
- Future Repairs: Having a few extra boards on hand can be useful for future repairs or replacements.
A typical waste factor for decking projects ranges from 5% to 15%. For complex deck designs or first-time installers, a higher waste factor (e.g., 10-15%) is recommended. For simple, rectangular decks, 5-10% might suffice.
How the Calculator Works
Our calculator performs the following steps:
- Calculates the total square footage of your deck (Length x Width).
- Calculates the square footage covered by a single composite board (Board Length x Actual Board Width in feet).
- Divides the total deck area by the area of one board to get the raw number of boards needed.
- Applies your specified waste factor to this raw number.
- Rounds up to the nearest whole board, ensuring you have enough material.
- Also provides the total linear feet of decking required.
Example Calculation:
Let's say you have a deck that is 12 feet long and 10 feet wide. You plan to use 16-foot long boards with an actual width of 5.5 inches, and you'll add a 10% waste factor.
- Deck Area: 12 ft * 10 ft = 120 sq ft
- Board Width in Feet: 5.5 inches / 12 inches/foot = 0.4583 feet
- Area per Board: 16 ft * 0.4583 ft = 7.333 sq ft
- Raw Boards Needed: 120 sq ft / 7.333 sq ft/board = 16.36 boards
- Boards with Waste (10%): 16.36 * (1 + 0.10) = 17.996 boards
- Rounded Up Boards: You would need 18 boards.
- Total Linear Feet: 18 boards * 16 ft/board = 288 linear feet.
Use this calculator to get a precise estimate for your project and build your dream deck with confidence!