When you’re gearing up for a roofing project, whether it’s a repair, replacement, or a new installation, one of the most critical questions is how many shingles you’ll need.

Roofing materials are typically sold by the square, and knowing the right amount ensures you don’t run short or end up with excess shingles.

In this straightforward guide, we’ll explore how to calculate the number of shingles required for a 1500 square foot roof.

Understanding Roofing Squares

Before we delve into the calculation, it’s essential to understand the concept of “roofing squares.” A roofing square is a unit of measurement equal to 100 square feet. Shingles are often packaged and sold by the square, making it a convenient way to estimate the materials you need.

Step-by-Step Calculation

Calculating the number of shingles you need for a 1500 square foot roof is a straightforward process. Follow these steps:

Step 1: Measure Your Roof

Start by measuring your roof’s square footage. To do this, multiply the length by the width of each individual plane or section of your roof and then add up the areas of all the sections. For example:

  • Front Slope: 30 feet x 20 feet = 600 square feet
  • Back Slope: 30 feet x 20 feet = 600 square feet
  • Two Side Slopes: 15 feet x 20 feet = 300 square feet each

Total Roof Area: 600 + 600 + 300 + 300 = 1800 square feet

Step 2: Convert to Squares

Since shingles are sold by the square, you need to convert your total square footage to squares. Divide the total square footage by 100:

Total Squares Needed: 1800 square feet ÷ 100 = 18 squares

Step 3: Account for Wastage

It’s a good practice to account for some wastage when purchasing shingles. Wastage can occur due to cutting shingles to fit edges, mistakes, or future repairs. A common rule of thumb is to add 10% to 15% to your total square count to accommodate for wastage.

Step 4: Calculate the Final Shingle Quantity

To calculate the final quantity of shingles needed, add the wastage to the total squares:

Total Shingles Needed: 18 squares + 15% wastage (2.7 squares) = 20.7 squares


For a 1500 square foot roof, you will need approximately 20.7 squares of shingles. Since you can’t purchase a fraction of a square, you would typically round up to 21 squares. This ensures you have enough material to complete your roofing project with a bit of extra for contingencies.


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.

Write A Comment