Roof size – it’s the key to understanding how much material you need and how long the project will take. But how do you calculate it without getting tangled in complex formulas?

We’re here to break it down in simple terms, step by step. Let’s learn how to calculate your roof size like a pro.

Step 1: Divide and Conquer

To find your roof size, start by dividing it into sections. Most roofs have two main parts: the main roof and any additional sections, like dormers or overhangs. Treat each section separately to make the math easier.

Step 2: Measure Length and Width

For each section, measure the length and width. Use a tape measure or a long piece of string to get accurate measurements. Imagine you’re laying a giant puzzle – you need to know the size of each piece.

Step 3: Calculate Square Footage

Now, multiply the length by the width for each section. This gives you the square footage of each part of your roof. For example, if one section is 20 feet long and 10 feet wide, it’s 20 x 10 = 200 square feet.

Step 4: Add it Up

Once you’ve calculated the square footage for each section, add them all together. This gives you the total square footage of your entire roof. It’s like putting all the pieces of your puzzle together to see the big picture.

Step 5: Don’t Forget Slopes

If your roof has different slopes or angles, you’ll need to calculate the square footage for each slope separately and then add them together. Think of it like measuring the sides of a mountain – you need to account for each slope.

Step 6: Include Overhangs

Don’t overlook the overhangs – those are the parts of the roof that extend beyond the walls of your house. Measure and calculate their square footage separately and add it to your total.

Step 7: Consider Pitch

If your roof is steep, you’ll need to factor in the pitch. This means you’ll have to account for the vertical rise of the roof in your calculations. It’s like measuring the height of a hill on your map.


Calculating your roof size is like solving a simple math problem. Break it down into sections, measure the length and width, multiply, and add it all up.

Don’t forget the slopes and overhangs, and adjust for pitch if needed. Once you’ve done the math, you’ll have a clear picture of your roof’s size, helping you plan your roofing project with confidence.

So, the next time you wonder how to calculate your roof size, remember these simple steps. You’ve got this!


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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