If your roof requires repair or replacement, one of the first things you’ll need to do is calculate the number of shingles you’ll need. This can seem like a daunting task, but it’s actually quite simple. All you need to do is measure the length and width of your roof and multiply those numbers to get the roof’s square footage. Once you have the square footage, you can estimate the number of shingles you’ll need by dividing this square footage of the roof by the number of square feet that each shingle covers.

For example, if your roof is 100 square feet and each shingle covers 20 square feet, you’ll need 5 shingles to cover the roof. Keep in mind that you’ll also need to factor in waste when calculating the number of shingles you’ll need, as you won’t be able to use every shingle you purchase. Most roofing professionals recommend ordering 10-15 percent more shingles than you’ll need to account for waste.

Read on for a more elaborate explanation of each step.

1. Get the Measurement of Your Roof Pitch

You need to take measurements of your roof’s pitch or roof slope. You will need the following:

  • Measuring tape
  • Level
  • Calculator

Start by measuring the width and length of your roof. Once you have those measurements, you’ll need to determine the pitch of your roof. To do this, you’ll need to measure the rise and run of your roof. The rise is the distance from the edge of your roof to the peak, while the run is the distance from the edge of your roof to the eave.

Once you have the rise and run, you can calculate the pitch by dividing the rise by the run. Once you know the pitch of your roof, you can calculate the area by multiplying the length and width of your roof by the pitch. 

2. Estimate the Roof Area

The roof pitch is the angle of your roof and can be used to estimate the square footage of your roof.

  1. Divide what you got by 12.
  2. Square the result.
  3. Add 1.
  4. Get the square root.
  5. Divide the result by 2.
  6. Multiply the square footage by the square root you got.

3. Get the Exact Roofing Area

To calculate the roof measurements, you need to know the length and width of your house first. After you have those measurements, you can calculate the area of your roof by multiplying the length and width. Once you have the area, you can calculate the square footage by multiplying the area by 2. You’ll need your measuring tape and ladder again to do this.

  1. Divide the roof pitch by 12.
  2. Square the answer.
  3. Add 1 to this result.
  4. Calculate the square root.
  5. Get the length and width of your house.
  6. Multiply the length by the width. This is the area.
  7. Multiply the result by the roof pitch.


Calculating the total roof area of a building is a relatively simple process that can be completed with a few basic measurements. The first step is to determine the length and width of the building. Once these dimensions are known, the next step is to calculate the pitch of the roof. With these pieces of information, the total roof area can be calculated by following the steps above. 

Do you need San Diego residential roofing? Rely on Pioneer Roofing Company. As a proud family-owned and operated business, we became one of the most well-respected and trusted roofing companies in the area. Get in touch with us today!