If you’re planning a roofing project or considering installing solar panels, knowing how to calculate your roof space is essential. Roof space calculation helps you determine the amount of materials you need and whether your roof is suitable for specific purposes. In this blog, we’ll walk you through the simple steps to calculate your roof space.


Your roof space is the total area of your roof’s surface. Accurate measurement ensures you can efficiently plan and budget for roofing or any other projects requiring space calculations. Here’s how to do it:

Step 1: Determine Your Roof’s Shape

Roofs come in various shapes, but the most common are:

  • Gable Roof: Shaped like an inverted V.
  • Hip Roof: Sloping gently upward from all sides.
  • Flat Roof: Mostly level with a slight slope for drainage.
  • Mansard Roof: Flat with a steeper slope near the edges.
  • Gambrel Roof: Similar to a mansard but with two slopes on each side.

Identifying your roof’s shape is crucial because it affects how you calculate its space.

Step 2: Measure Roof Length and Width

For a simple gable roof, you’ll need to measure its length and width. If you have a more complex roof shape, break it down into sections that are easier to measure. Use a long measuring tape or laser distance measurer for accuracy.

Step 3: Calculate Roof Space

Once you have your measurements, calculating the roof space is straightforward:

  1. For a Gable Roof: Multiply the length and width of one side of the roof and then double that result. This accounts for both sides of the gable roof.
  2. For a Hip Roof: Measure the length and width of the entire roof and multiply these measurements together.
  3. For a Flat Roof: Multiply the length by the width.
  4. For a Mansard Roof: Measure the length and width of the flat part of the roof, multiply them, and then double the result since mansard roofs have two slopes on each side.
  5. For a Gambrel Roof: Similar to a mansard, measure the length and width of the flat part, multiply them, and double the result.


Let’s say you have a gable roof with a length of 40 feet and a width of 30 feet.

  • Roof Space = (40 ft × 30 ft) × 2 = 2,400 square feet.

If you have a hip roof with a length of 50 feet and a width of 40 feet:

  • Roof Space = 50 ft × 40 ft = 2,000 square feet.

Remember, these are simplified calculations for basic roof shapes. If your roof has multiple sections or intricate designs, break it down into smaller sections and calculate each separately before adding them together.

Why Calculating Roof Space Matters

  • Material Estimation: Knowing your roof space helps you calculate the amount of roofing materials required, such as shingles, underlayment, and flashing.
  • Project Planning: It’s crucial for planning any projects involving your roof, like solar panel installation, roof gardens, or chimney placement.
  • Cost Estimation: Accurate measurements allow for more precise cost estimates, helping you budget effectively.


Calculating your roof space is a fundamental step in any roofing or related project. Whether you have a simple gable roof or a more complex design, measuring your roof’s length and width and applying the appropriate formula for its shape will provide you with an accurate estimate. This knowledge empowers you to plan and budget effectively for your roofing or home improvement endeavors.


As a civil engineer and roofer, I love to share the experience that I have gained through the last couple of years. In the roofing industry, practical experience is a very crucial fact that can help you a lot. Hence, I want to help you with my blog.

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