Calculate Roof Area

*Our roofing calculator provides an estimate for up-and-over roofing. Additional architectural features like awnings and dormers may impact the final estimation.

How is the area of a roof calculated?

The area of any surface is calculated by multiplying length by width. Base length and base width measurements are required to accurately calculate the square footage of the roof. Base length refers to the distance from one corner of the roof to another, following the long side of the home, while base width is the distance from one corner of the roof to another along the short side of the home. 

For a flat roof, the calculation is nearly done at this point. However, many roofs are positioned at an angle, which means one last measurement is required to calculate the area of the roof: roof pitch.

What is roof pitch?

Roof pitch refers to the slope or angle of a roof. Flat roofs have a very low pitch, compared to gable roofs, which have a medium to steep pitch. The greater the pitch, the larger the surface of the roof tends to be. Therefore, a home with a steep pitch will require more roofing material than a home with a low roof pitch. 

How is roof pitch calculated?

Pitch is calculated by dividing the “rise” of a roof by its “run”. Rise refers to the vertical distance between the top of the house wall to the peak of the roof, whereas run refers to the horizontal distance between the outer edge of the roof to the center of the home.

Since roof run in the U.S. is calculated using 12 inches as a baseline, roof pitch is categorized as “X out of 12” with X representing the roof rise measurement. For example, a 5-inch roof rise equates to a roof pitch categorized as “5” or “5/12” depending on the calculator tool used.  

How much roofing material do I need?

To ensure you have an adequate supply of roofing material for your roof replacement, you’ll need to know the area of your roof in square feet, plus an additional 15% for waste allowance. 

How to Calculate Square Footage of a Roof

[Base Length in Ft.] x [Base Width in Ft.] x [Pitch] = Roof Area in Sq. Ft

[Roof Area in Sq. Ft] x 1.15 = Total Roofing Material in Sq. Ft

[Total Roofing Material in Sq. Ft] / 100 = # of Roof Squares Needed*

*Round up to the nearest whole number 

Hear From Our Customers

Homeowners across the DMV and New England are trusting Long Roofing for home improvement services. With a 4.6-out-of-5-star rating based on over 5,000 reviews on GuildQuality, we’ve earned the coveted Guildmaster award—an honor granted to companies that provide exceptional service.

Dana P. | Rockville, MD

The installers were professional, cleaned up my yard, I have yet to find a nail! Very friendly and did a quality job...

Jacquelyn W. | Bowie, MD

Josh was exceptional in his knowledge and very professional.

Natchanon K. | Burke, VA

We were very appreciative in how quickly Long Roofing was able to accomplish the project. The labor crew came on two...

| Washington, DC

They explained everything to me and I felt that I got the best because of what they offered.

Jennie W. | Washington, DC

Teresa Butts at Long Roofing made me feel comfortable with the process and understand what I was receiving.

Satoshi I. | Alexandria, VA

The responsiveness was quick and thorough as I had questions regarding the finishing of the roof and when I inquired about...

Long Roofing Service Areas

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Corporate Office 8530 Corridor Rd
Savage, MD 20763

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Regional Office 300 Myles Standish Blvd
Taunton, MA 02780

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