The 2 Minute Roof Pitch Area Calculator

May 31 2019   04 PM  

If you’re trying (and struggling) to work out the surface area of a sloped roof we’ve got you covered. As a roofer we may need the surface area to order materials or maybe we’re quoting a job.

In Australia we measure pitch in degrees, whilst in Americans do it as a ratio over 12. However it doesn’t really matter in the end, all that matters is that we receive the correct surface area in the we can quote and order materials correctly.

In 4 quick steps we’ll know the surface area of the sloped roof.

1. Find the pitch


2. Find the plan area (from a top down view)


3. Find the multiplier factor


4. Do the calculation


1. Find the Pitch:

In most cases you’ll actually have the pitch, however if you need to know it. Here’s what it is, and how to find it.

Australians: This will be given as an angle, eg 25°, 22.5°, etc


Americans: Express their pitch as a ratio over 12, meaning how much it rises over 12 inches. Eg if it rises 6 inches over 12 inches, then Pitch = 6:12

(Credit: SketchAmdCalc)

2. Find the plan area (from a top down view)

Head over to

Upload your set of plans, if you don’t have plans and are redoing an existing roof you can use this google maps trick

Set your scale, then imply use the polygon or rectangle tool to measure the area.


3. Find the multiplier factor

Use this table: Plugin your pitch and get your multiplier.

roof pitch calculator


4. Do the Calculation

Surface Area of Sloped Roof = (Plan Area) x (Multiplier Factor)

Surface Area of Sloped Roof = 226.92 x 1.0642

= 241.48 meters squared

And there you have it, 4 easy steps to calculating roof areas! Is there anything else you’d like to know? Let us know in the comments below.