Exterior Square Footage Calculator
Use this calculator to estimate the total exterior surface area of your building, which is essential for planning projects like painting, siding installation, or insulation. Accurate measurements help ensure you purchase the right amount of materials and budget effectively.
What is Exterior Square Footage?
Exterior square footage refers to the total surface area of a building's outer shell, including walls, gables, and the roof. It's a critical measurement for various home improvement projects, as it directly impacts the quantity of materials needed and the overall cost.
Why is Exterior Square Footage Important?
- Painting: Knowing the exterior square footage helps you determine how much paint you'll need, preventing over-purchasing or multiple trips to the store.
- Siding: Whether you're installing vinyl, wood, or fiber cement siding, an accurate measurement ensures you order the correct amount of panels or planks.
- Insulation: For exterior wall or roof insulation, this measurement guides material estimates.
- Material Estimation: Beyond paint and siding, it's useful for estimating stucco, brick, or stone veneer quantities.
- Budgeting: Material costs are often calculated per square foot, so an accurate total helps in creating a realistic budget.
How to Use the Calculator
Our Exterior Square Footage Calculator simplifies the process of estimating your building's surface area. Here's a breakdown of the inputs:
- Building Length (feet): The longest side of your rectangular building footprint.
- Building Width (feet): The shorter side of your rectangular building footprint.
- Wall Height (feet): The vertical height of your exterior walls, from the ground or foundation to where the roof structure begins.
- Roof Pitch Rise (e.g., 6 for a 6/12 pitch): This describes the steepness of your roof. A "6/12" pitch means the roof rises 6 inches vertically for every 12 inches it extends horizontally. Enter only the "rise" number (e.g., 6).
- Number of Gable Ends (0, 1, or 2): Gables are the triangular sections of wall at the end of a pitched roof. Most simple rectangular houses with a gable roof have two gable ends. A hip roof has zero.
- Number of Windows: The total count of windows on your exterior.
- Average Window Width (feet): The typical width of your windows. If they vary significantly, you might calculate separate areas or use a weighted average.
- Average Window Height (feet): The typical height of your windows.
- Number of Doors: The total count of exterior doors.
- Average Door Width (feet): The typical width of your exterior doors.
- Average Door Height (feet): The typical height of your exterior doors.
Understanding the Calculation
The calculator works by summing the areas of the walls, gables, and roof, then subtracting the areas of windows and doors. This provides a net surface area for material estimation.
- Wall Area: Calculated as the perimeter of the building multiplied by the wall height.
- Gable Area: Each gable is treated as a triangle, with its base being the building width and its height derived from the roof pitch.
- Roof Area: The calculator determines the roof's surface area by considering the building's footprint and applying a multiplier based on the roof pitch. A steeper pitch results in a larger surface area.
- Deductions: The combined area of all windows and doors is subtracted from the total to give you a more accurate surface area for materials that won't cover these openings.
Example Calculation
Let's calculate the exterior square footage for a house with the following dimensions:
- Building Length: 40 feet
- Building Width: 30 feet
- Wall Height: 10 feet
- Roof Pitch Rise: 6 (for a 6/12 pitch)
- Number of Gable Ends: 2
- Number of Windows: 10 (average 3 ft wide x 4 ft high)
- Number of Doors: 2 (average 3 ft wide x 7 ft high)
1. Wall Area: 2 * (40 ft + 30 ft) * 10 ft = 1400 sq ft
2. Gable Area:
- Gable Height: (30 ft / 2) * (6 / 12) = 15 ft * 0.5 = 7.5 ft
- Area per Gable: 0.5 * 30 ft * 7.5 ft = 112.5 sq ft
- Total Gable Area: 2 * 112.5 sq ft = 225 sq ft
3. Roof Area:
- Pitch Multiplier (for 6/12): √(1 + (6/12)2) ≈ 1.118
- Roof Footprint: 40 ft * 30 ft = 1200 sq ft
- Total Roof Surface Area: 1200 sq ft * 1.118 ≈ 1341.6 sq ft
4. Deduction Area (Windows & Doors):
- Windows: 10 * (3 ft * 4 ft) = 10 * 12 sq ft = 120 sq ft
- Doors: 2 * (3 ft * 7 ft) = 2 * 21 sq ft = 42 sq ft
- Total Deduction: 120 sq ft + 42 sq ft = 162 sq ft
5. Total Exterior Square Footage: 1400 sq ft (Walls) + 225 sq ft (Gables) + 1341.6 sq ft (Roof) – 162 sq ft (Deductions) = 2804.6 sq ft
Tips for Accurate Measurement
- Use a reliable tape measure: A long, sturdy tape measure is essential.
- Measure twice: Double-check all your measurements to minimize errors.
- Account for irregularities: While this calculator assumes a rectangular building, for complex shapes, you may need to break down the exterior into simpler geometric forms and sum their areas.
- Consider overhangs: While the calculator estimates the main roof surface, remember that roof overhangs might require additional material for fascia or soffit, which are not included in this calculation.