Easily calculate the total square footage of your deck project to help with material estimation and planning.
Deck Area Calculator
Enter the longest dimension of your deck in feet.
Enter the shorter dimension of your deck in feet.
If your deck has multiple rectangular parts, enter the total number of sections.
Enter the length of the first section.
Enter the width of the first section.
Your Deck Area Results
— sq ft
Section 1 Area: — sq ft
Total Area of All Sections: — sq ft
Estimated Board Feet (for decking boards): — board ft
Formula: Total Deck Area = Sum of (Length of Section * Width of Section) for all sections.
Estimated Board Feet = Total Deck Area * 1.1 (assuming 10% waste/cuts).
Deck Area Breakdown
Deck Section Area Distribution
Deck Area Data Table
Section
Length (ft)
Width (ft)
Area (sq ft)
Section 1
—
—
—
Deck Section Dimensions and Calculated Areas
What is Deck Square Footage?
Deck square footage refers to the total surface area of a deck, measured in square feet. It's a fundamental metric for anyone planning to build, renovate, or simply understand the size of an outdoor living space. This measurement is crucial for accurately estimating the amount of materials needed, such as decking boards, railings, and concrete for footings, as well as for budgeting purposes. Understanding your deck square footage helps in comparing different design options and ensuring your project stays within scope and budget.
Who should use it? Homeowners planning a new deck, contractors estimating project costs, DIY enthusiasts calculating material needs, and anyone looking to understand the scale of their outdoor space will find deck square footage calculations invaluable. It's a foundational step in any deck project, from simple platforms to complex multi-level structures.
Common misconceptions: A common mistake is assuming a deck's square footage is simply its overall length times its overall width, especially for irregularly shaped decks. Many decks are L-shaped, have cutouts for trees, or consist of multiple connected rectangular sections. Failing to account for these complexities can lead to significant underestimation of material needs. Another misconception is that square footage directly translates to cost without considering material type, complexity, or labor.
Deck Square Footage Formula and Mathematical Explanation
Calculating deck square footage is straightforward, especially for simple rectangular decks. For more complex shapes, it involves breaking the deck down into simpler geometric components, typically rectangles, and summing their areas.
For a single rectangular deck:
The formula is simple multiplication:
Deck Area = Deck Length × Deck Width
For decks with multiple rectangular sections:
If your deck is composed of several distinct rectangular parts (e.g., a main area and an attached smaller section), you calculate the area of each section individually and then sum them up.
Total Deck Area = Σ (Length of Sectioni × Width of Sectioni)
Where 'i' represents each individual section of the deck.
Estimated Board Feet:
While square footage gives the surface area, decking is typically sold by linear foot or board foot. A common rule of thumb is to add a waste factor (usually 10-15%) to account for cuts, mistakes, and unusable pieces. Board feet are a measure of volume (1 board foot = 1 inch thick x 12 inches wide x 1 foot long). For standard 5/4″ x 6″ decking boards, the conversion is roughly 4 linear feet per square foot of deck surface, but using a board foot estimate with waste is more practical for purchasing.
Estimated Board Feet ≈ Total Deck Area × 1.1 (for 10% waste)
Variable Explanations
Variable
Meaning
Unit
Typical Range
Deck Length
The longest dimension of a rectangular deck or section.
Feet (ft)
1 to 100+
Deck Width
The shorter dimension of a rectangular deck or section.
Feet (ft)
1 to 100+
Number of Sections
The count of distinct rectangular areas making up the total deck.
Count
1 to 10+
Length of Sectioni
The length of an individual rectangular section.
Feet (ft)
1 to 100+
Width of Sectioni
The width of an individual rectangular section.
Feet (ft)
1 to 100+
Deck Area
The total surface area of the deck.
Square Feet (sq ft)
10 to 1000+
Estimated Board Feet
Approximate volume of lumber needed for decking boards, including waste.
Board Feet (board ft)
10 to 1000+
Practical Examples (Real-World Use Cases)
Example 1: Simple Rectangular Deck
Scenario: A homeowner wants to build a standard rectangular deck in their backyard.
Inputs:
Deck Length: 16 ft
Deck Width: 10 ft
Number of Sections: 1
Length of Section 1: 16 ft
Width of Section 1: 10 ft
Calculation:
Area of Section 1 = 16 ft * 10 ft = 160 sq ft
Total Deck Area = 160 sq ft
Estimated Board Feet = 160 sq ft * 1.1 = 176 board ft
Interpretation: The homeowner needs approximately 160 square feet of deck surface. For purchasing decking boards, they should plan for around 176 board feet to account for cuts and potential waste. This figure helps in getting quotes from lumber suppliers.
Example 2: L-Shaped Deck with Multiple Sections
Scenario: A homeowner is designing a more complex L-shaped deck that wraps around a corner of their house.
Inputs:
Deck Length: (Not directly used for multi-section calculation, but gives overall span)
Deck Width: (Not directly used for multi-section calculation)
Number of Sections: 2
Length of Section 1: 20 ft
Width of Section 1: 12 ft
Length of Section 2: 10 ft
Width of Section 2: 8 ft
Calculation:
Area of Section 1 = 20 ft * 12 ft = 240 sq ft
Area of Section 2 = 10 ft * 8 ft = 80 sq ft
Total Deck Area = 240 sq ft + 80 sq ft = 320 sq ft
Estimated Board Feet = 320 sq ft * 1.1 = 352 board ft
Interpretation: This L-shaped deck requires a total surface area of 320 square feet. The material estimate for decking boards, including waste, is approximately 352 board feet. This detailed calculation is vital for accurate material purchasing and project costing for complex designs.
How to Use This Deck Square Footage Calculator
Using our Deck Square Footage Calculator is designed to be simple and intuitive. Follow these steps:
Identify Deck Sections: If your deck is a simple rectangle, you only need to input the length and width for Section 1. If your deck has multiple rectangular parts (e.g., a main platform and an attached smaller area), you'll need to measure the length and width of each section separately.
Enter Dimensions:
Input the 'Deck Length' and 'Deck Width' for the primary section (or the overall dimensions if it's a single rectangle).
Enter the 'Number of Sections' if your deck is not a single rectangle.
For each section (Section 1, Section 2, etc.), input its specific 'Length' and 'Width' in feet.
Calculate: Click the "Calculate Area" button.
Review Results: The calculator will display:
Primary Result: The total square footage of your entire deck.
Intermediate Values: The calculated area for each section entered, the total area of all sections combined, and an estimate of the board feet needed for decking materials (including a waste factor).
Formula Explanation: A brief description of how the calculation was performed.
Data Table & Chart: A visual breakdown of your section dimensions and areas.
Copy Results: If you need to save or share the information, click "Copy Results". This will copy the main result, intermediate values, and key assumptions to your clipboard.
Reset: To start over or try different dimensions, click the "Reset" button.
Decision-Making Guidance: The total square footage is your primary figure for planning. Use the estimated board feet to get accurate quotes for lumber. Comparing the square footage against your available space and budget will help you finalize your deck design.
Key Factors That Affect Deck Square Footage Calculations
While the calculation itself is mathematical, several real-world factors influence how you measure and use deck square footage:
Deck Shape Complexity: Irregular shapes (curves, octagons, multiple angles) require more advanced geometry or breaking down into smaller, calculable shapes. Our calculator handles multiple rectangles, but complex curves would need different methods.
Attached vs. Freestanding: Whether the deck attaches to the house or stands alone doesn't change the square footage calculation but impacts structural requirements and potentially permits.
Multi-Level Decks: If your deck has multiple levels, each level's square footage must be calculated separately and then summed for a total surface area.
Cutouts and Obstructions: Areas cut out for trees, existing structures, or complex railings might slightly reduce the usable square footage, though often the overall footprint is still used for material estimation.
Railing and Stair Areas: The square footage calculation typically only covers the flat walking surface. Railings and stairs add to the overall project footprint but aren't usually included in the primary deck surface area calculation.
Waste Factor Selection: The percentage added for waste (e.g., 10% for board feet) is an estimate. Complex patterns, board width, and installer skill can affect the actual waste. It's often better to slightly overestimate than underestimate.
Material Widths: While we calculate based on desired dimensions, the actual width of decking boards (e.g., nominal 6-inch boards are actually ~5.5 inches) can slightly affect the number of boards needed, though the square footage remains the primary metric.
Permitting Requirements: Local building codes may have specific definitions or requirements regarding how deck area is measured, especially for decks over a certain size or height, which could influence permit applications.
Frequently Asked Questions (FAQ)
Q1: What is the difference between deck square footage and linear footage?
A: Square footage measures the total surface area (length x width). Linear footage measures length along a single dimension, often used for materials like railings or trim. Decking boards are often sold by linear foot or board foot, but the initial calculation is based on square footage.
Q2: Do I need to include the area under stairs in my deck square footage?
A: Typically, deck square footage refers to the main walking surface. The area occupied by stairs is usually calculated separately for structural and material planning, but not added to the primary deck surface area.
Q3: How accurate is the "Estimated Board Feet" calculation?
A: The estimated board feet calculation (Total Area * 1.1) is a common industry guideline assuming about 10% waste. Actual waste can vary based on the complexity of the deck design, the skill of the installer, and the specific dimensions of the lumber purchased.
Q4: My deck isn't a perfect rectangle. How do I calculate its square footage?
A: For decks with multiple rectangular sections, break the deck down into individual rectangles, calculate the area of each, and sum them up. For curved or highly irregular shapes, you might need to approximate using simpler shapes or consult a professional.
Q5: Should I round my measurements up?
A: It's generally advisable to round your measurements up to the nearest foot or half-foot when calculating materials, as it's better to have a little extra lumber than to run short. This calculator uses the exact numbers you input.
Q6: Does deck square footage affect building permits?
A: Yes, in many jurisdictions, decks exceeding a certain square footage threshold (e.g., 120 sq ft or 200 sq ft) or height may require a building permit. Always check with your local building department.
Q7: How does the number of sections affect the calculation?
A: The number of sections allows you to accurately calculate the area of complex decks by summing the areas of individual rectangular parts. Each section's length and width are multiplied to find its area, and these are then added together.
Q8: Can I use this calculator for composite decking?
A: Yes, the square footage calculation is the same regardless of the material (wood, composite, PVC). The "Estimated Board Feet" is more relevant for traditional lumber; for composite, you'd typically calculate based on square footage and the specific product's coverage.