2 Ways to Calculate the Square Footage of Your Roof

When you’re planning to begin a roofing project, you may find that you need to know the square footage of your roof. This will assist you to get exact quotes for your roof project, as pros will know exactly how much roofing material will be required.

In order to determine the square footage of your roof, just follow the guidelines listed below.

Assessing the square footage of your roof

There are 2 distinct methods of figuring out the square footage of your roof.

1. House footprint

For the first technique, you’ll need to find out the slope or pitch angle of your roof. Once you know this, you can just multiply this angle by the base area of your house.

That being said, working out the pitch angle of a roof is tricky. Because of this, we recommend using the second approach to come up with an estimate for the square footage of your roof.

2. Measuring each plane

With this method, you’ll measure each plane of the roof separately to come up with the total square footage. In this case, plane means flat surface.

For a shed roof with a singular flat surface, you simply need to measure the square footage of that surface. In order to accomplish this, multiply the width by the height.

Via Curtis Lumber

For instance, in the graphic above, you would multiply A by B. If the width of the roof was 8 feet, and the height was 12, then multiply 8 by 12. This gives a total square footage of 96 ft2.

Gable roofs

When it comes to a gable roof, which has 2 rectangular planes, you multiply the width and length of each plane together, then add the result together. If each plane had a width of 16 feet, and a height of 12, you can do 16×12, which equals 192. Because this is for only one of the planes, you then add the two planes together, which is 192 +192. So, the total roof square footage would be 384 ft2.

Via Curtis Lumber

Hip roofs

Hip roofs are a bit trickier. With 4 planes, there are extra planes to measure.

For the triangle ends of the roof, multiply the height by the width of the triangle, and then divide by 2. If the height of the triangle is 10 feet, and the width is 12, then the equation would be 10 times 12, and then halved, for 60ft2.

Via Home Stratosphere

When it comes to the 2 trapezoids, in the roof pictured above, you add the length of the bottom of the roof to the length of the top. If the base was 16ft long, and the length of the top was 10ft, you’d have 26ft. You then multiply 26 by the height of the roof. If the height of the roof was 10ft, you’d multiply that by the 16ft, for 260ft. Finally, divide the result by 2. So, take 260ft and divide by 2 for 130ft2.

To add the total of the hip roof, just add all 4 planes together. This means calculating 60+60+130+130, for a total square footage of 380ft2.

Step-by-step

For a step-by-step guide to a hip roof:

  1. Measure the first trapezoid plane: (16+10) x 10 ÷ 2 = 130ft2
  2. Measure the second trapezoid plane: (16+10) x 10 ÷ 2 = 130ft2
  3. Measure the first triangular plane: (10x 12) ÷ 2 = 60ft2
  4. Measure the second triangular plane: (10×12) ÷ 2 = 60ft2
  5. Add all of the planes together: 130 + 130 + 60 + 60 = 380ft2

This approach of calculating the square footage is appropriate for all forms of roof. When measuring more complex roofs, simply add up all the different planes, including dormers and other extra parts of the roof.

Hopefully, these guidelines to measuring the square footage of your roof give you an easy technique to provide correct measurements to roofing pros. If you’re looking to find roofing pros in your area, just fill out the quick form below. We’ll match you with up to 4 local roofing pros.


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