How to Measure the Square Footage of your Roof

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When you’re looking to start a roofing project, you may find that you need to know the square footage of your roof. This will help you get accurate quotes for your roof project, as companies will know exactly how much roofing material will be needed.

To estimate the square footage of your roof, simply follow the instructions below.

Measuring the square footage of your roof

There are two different methods of measuring the square footage of your roof.

1. House footprint

For the first method, you’ll need to know the slope or pitch angle of your roof. If you know this, you can simply multiply this angle by the base area of your home.

However, figuring out the pitch angle of a roof is difficult. So, we recommend using the second method to come up with an estimate for the square footage of your roof.

2. Measuring each plane

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

So, for a shed roof with a single flat surface, you just need to work out the square footage of that surface. To do this, multiply the width by the height.

Via Curtis Lumber

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

Gable roofs

For a gable roof, with 2 rectangular planes, you multiply the width and length of each plane together, then add the result together. For example, if each plane had a width of 16 feet, and a height of 12, you can do 16×12, which equals 192. As this is for only one of the planes, you then add the two planes together, meaning 192+192. So the total roof square footage would be 384 ft2.

Via Curtis Lumber

Hip roofs

Hip roofs are a little bit trickier. With 4 planes, there are more surfaces to measure.

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

Via Home Stratosphere

For the two trapezoids, in the roof pictured above, you add the length of the bottom of the roof to the length of the top. For example, 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

So, 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: (10 x 12) ÷ 2 = 60ft2
  4. Measure the second triangular plane: (10 x 12) ÷ 2 = 60ft2
  5. Add all of the planes together: 130 + 130 + 60 + 60 = 380ft2

This method of measuring the square footage works for all types of roof. For more complex roofs, simply add up all the different planes, including dormers and any other extra parts of the roof.

Hopefully, this guide to measuring the square footage of your roof gives you an easy way to give accurate 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.