How to Measure a Roof For Shingles

Learn how to measure a roof for shingles roof like a pro. Get accurate estimates with our guide from an experienced roofing contractor.
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Reviewed by JC Sanjuan — General and roofing contractor with over a decade of experience in residential and commercial construction. He specializes in project management, quality workmanship, client satisfaction, and solving roofing challenges.

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Not sure how to measure a roof for a shingle replacement and need help figuring out where to start? Whether you’re a professional in the field or a homeowner looking to get an estimate, getting the measurements right is the first step. In this article, we’ll walk you through the process of measuring a roof, just like a seasoned roofing and general contractor would.

Steps to How to Measure a Roof for Shingles

Step 1: Research and Preparation

The first step to measure a roof is to get some basic info about the house. I like to start by looking up the home’s address on Google Maps. This gives you a bird’s-eye view of the roof so you can see its shape. It’s a great way to know a bit about the roof before you even get there.

How to measure a roof for shingles This is a photo of a house being calculated for roof measurements using Google Maps

Step 2: Visual Assessment and Sketch

After you know a bit more of your roof from Google Maps, the next step is to go assess it yourself from the ground. Take a good look at how the roof is shaped and if it has any special features like ridges or different sections. I always bring a notepad and draw the roof as best as I can to make sure I get it right. If the roof is just a simple rectangle, then that’s what I draw. Knowing the roof’s shape really well helps you get the measurements right.

How to measure a roof for shingles This is a photo of a house being calculated for roof measurements

Step 3: Safety Precautions

Safety is really important when you’re working on a roof. Before I climb up, I make sure the ladder is stable and all my safety gear is ready. I wear the right shoes and bring along a notepad, pencil, and tape measure. In this job, you can’t take chances with safety.

Step 4: Taking Measurements

How to measure a roof for shingles This is a contractor measuringridge of roof

With safety ensured, I start the actual measurement process. Here’s how it’s done:

  1. Measuring the Ridge: I begin by measuring the length of the ridge, going from one end of the roof to the other. For instance, if it measures 60 feet, I note that down.
  2. Measuring Eave to Ridge: Next, I measure from the eave to the ridge, both on one side and the opposite side. Let’s assume it’s 20 feet on each side. I jot down these measurements.
  3. Calculating Area: Let’s assume we have a rectangular roof, I multiply the length and width. In this case, it’s 60 feet by 40 feet, giving us an area of 2400 square feet.

Step 5: Detailed Measurements

How to measure a roof for shingles This is a sketch with measurements

It’s essential to account for all aspects of the roof. I also measure the sides — which are the eaves and rakes around the roof. This helps me figure out the perimeter of the house. Every detail is carefully noted on my notepad, and I label my sketch for reference.

Step 6: Crunching the Numbers

After gathering all the measurements, I return to solid ground and start working on the calculations. Here’s how it’s done:

  1. Section Breakdown: I break down the roof into sections based on its shape and features. For example, if we have three sections — A, B & C with areas of 2048 square feet, 576 square feet, and 1170 square feet, I add them up: 2048 + 576 + 1170 = 3,790 square feet.
  2. Converting to Squares: In the roofing industry, we typically work with squares, where 100 square feet equals one square. So, our 3,790 square feet becomes 37.94 squares, or 38 squares.

Step 7: Accounting for Extras

To provide a close estimate for a roofing project, it’s important to consider the waste factor and additional materials. This usually amounts to around 10 to 15 percent depending if it is a gable or hip roof, or if it has too many sections. These extra materials include ridge caps, hip caps, and starters. I add this factor to the total square measurement.

Step 8: Final Calculation

Adding the waste factor and extra materials could turn that 38 square to an additional 3 or 4 squares. The total turning out to be approximate 43 squares. This final figure is key, as most roofing professionals charge based on the price per square. Now you have a solid estimate of how much your roofing project will cost.


Measuring a roof accurately is the foundation of any successful roofing or general contracting project. As a seasoned roofing and general contractor, these are the steps I follow to ensure precision and reliability in my measurements.

Remember, accurate measurements lead to accurate estimates, resulting in a successful and cost-effective roofing project. If you have any questions or need further guidance on roofing matters, don’t hesitate to reach out.

There are other methods on how to measure a roof for shingles replacement. I’ll be writing other articles on those soon, so be on the look out.


Atcheson, Daniel. Roofing Construction & Estimating. Craftsman Book Company, 2023.

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