Determining your roof size is a fundamental step in any roofing project. Whether you’re planning to replace shingles, install a metal roof, or carry out repairs, knowing your roof’s size is crucial for buying the right amount of materials and ensuring a successful outcome. In this blog, we’ll guide you through the process of measuring your roof size in a simple and straightforward way.

Why Measure Your Roof Size?

Before we dive into the “how,” let’s understand why knowing your roof size matters:

  1. Materials: Buying too much or too little roofing material can be costly and inconvenient. Accurate measurements ensure you purchase just the right amount.
  2. Budgeting: Knowing your roof size helps you estimate costs accurately, preventing budget overruns.
  3. Efficiency: It ensures a smoother roofing project by reducing the chances of running out of materials or ordering excess.

Measuring Your Roof Size

Follow these steps to measure your roof size accurately:

  1. Divide Your Roof: If your roof has a simple, rectangular shape, divide it into sections. For complex roofs with multiple angles or sections, break it down into smaller, manageable areas. Measure each section separately.
  2. Measure Length and Width: Use a tape measure to determine the length and width of each section. Measure from eave to ridge for length and from gable end to gable end for width. Multiply the length and width for each section to calculate its square footage.
  3. Add Sections: If you have multiple sections, add their square footages together to get the total roof size. Don’t forget to account for any overhangs or roof features like dormers.

Accounting for Pitch

Roofs are rarely perfectly flat. Most have a slope or pitch. To account for pitch, follow these guidelines:

  1. Use the Pythagorean Theorem: To calculate the effective square footage of a sloped roof, you’ll need to use the Pythagorean Theorem. Measure the horizontal distance (run) and the vertical distance (rise) to the highest point of the roof, and calculate the hypotenuse. This represents the true square footage of the sloped area.
  2. Multiply by Pitch Factor: Roofing materials are typically sold based on square footage, so you’ll need to convert the sloped area to flat area square footage. Use a pitch factor, which is a multiplier that corresponds to your roof’s pitch. For example, a 6/12 pitch has a pitch factor of 1.12. Multiply the true square footage by this factor to get the flat area square footage.

The Verdict

Measuring your roof size might seem like a challenging task, but it’s crucial for a successful roofing project.

Accurate measurements save you time, money, and ensure you have the right materials on hand. If you’re unsure about any step in the process, consider consulting with a professional roofer who can provide expert guidance.


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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