Roof Surface Area Calculator

By Jack Gray, Roof Online Editor • Updated January 24, 2024

A satellite image of a roof divided into sections with simple dimensions to make it easier to use our roof area calculator.
It’s easier to calculate your total roof area if you break the roof down into sections with simple dimensions.


This Roof Area Calculator is designed to simplify the process of determining the surface area of a roof.

Whether you’re a professional in the construction industry or a homeowner planning a roofing project, this calculator offers an easy-to-use interface to input the dimensions of your roof sections.

You enter the width, length, and slope of each section, and the calculator computes the footprint area of the roof section, the roof pitch multiplier that applies for the given slope, and the actual surface area of the roof section. The roof’s surface area is calculated in both square feet and square meters.

You can get the dimensions of your roof sections by physically measuring the building, or you can get usefully accurate measurements from a satellite image like the picture above. For help with this, see our article on how to measure a roof with Google Earth.

If you’re not sure what the slope of your roof is and you want to measure it, in either degrees or standard roof pitch, we recommend this slope finder on Amazon. It’s very inexpensive and very accurate.

We also made a roof pitch visualizer that you can use. See below.

If your building is in the shape of a simple square or rectangle, you’ll only need to enter the width, length, and slope for the whole building, but the calculator also allows you to add the dimensions for multiple roof sections and then calculate their combined total area, which is useful for more complex roof shapes.

You can select feet or meters for your unit of measurement, and you can enter your roof slope in either standard roof pitch (X-in-12) or degrees.

Roof Area Calculator

Roof Area Calculator

Roof Area Calculator

Width of Roof Section:
Length of Roof Section:
Roof Slope:

If you are interested in learning more about the details and the math behind roof area calculations, please see our article How to Calculate Roof Area with Pitch and Footprint.

Roof Pitch Visualizer

If you're not sure what your roof pitch is, you can go outside and take a look at your roof and then play around with this roof pitch visualizer until you get something that looks close. It may not be exact, but if you get close, the pitch value you get will be useful enough to get you within a couple of percentage points when calculating your roof area.

Dynamic House Drawing with Extended Roof

Roof Pitch Visualizer

X-in-12 Roof Pitch
X Degrees

Related Articles

  1. Hip and Valley Factor Chart
  2. How to Calculate the Area of a Sloped Roof
  3. Minimum Required Roof Pitch for Every Roofing Material
  4. Rafter Manual: Using the Square • Rafter Lengths • Rafter Angles
  5. Roof Pitch Multiplier Chart
  6. Roof Pitch to Degrees  Degrees to Roof Pitch • Reference Charts
  7. Ways to Express Roof Slope: Pitch, Degrees, and Percentage