3 Ways to Calculate Roof Pitch

A few years back, a tropical storm damaged our roof. Since the insurance company would only pay for one half of the roof damage, we decided to re-shingle the roof ourselves. In order to find the area of the roof so we could buy supplies, we used the roof pitch, or angle, because it is safer than climbing up onto the roof to take physical measurements.

Roof pitch measures the slope or steepness of your roof. Pitch is found by comparing the run, or base, of the roof to the rise. once you have the base, rise and pitch measurements, there is a formula that you plug them into to calculate the area. If math isn’t your forte, there are also sites online that will calculate the area for you. There are three main methods of determining roof pitch.

Find Your Pitch On Construction Plans

If you are lucky enough to be the first owner of your house, you will likely still have a copy of the house plans. If not, you may find a copy at your local courthouse. In those plans, the roof pitch and measurements are found on the roof construction page. If any changes have been made to your house since it was built, you may need to see the amended plans.

Tools to Determine Roof Pitch

If it’s not possible to get the original construction plans, there are tools that can help you measure the pitch of your roof. We used something called a roof angle finder. By placing it under the eaves, we were able to get an accurate measurement. It even had a built-in graph for interpretation of the readings. Ours was less than $20, but they range in price from simple tools with no bells and whistles for under $10 to professional models at over $50. We got ours at a home improvement store, but you can also buy them online.

Go Back to Basics

If you know how to use a level and framing square, you can use the two together to measure the pitch of your roof, which will give you a more accurate reading. Place the framing square body level on the uphill side of the roof. Be sure the tongue is facing up. The level will go tightly against the framing square and the roof. Move the two together until the level is plumb, then place a mark on the level where it meets the framing square. Measure that distance and divide by two for the pitch. This is hard to understand in text, but Pro Framer has a detailed instruction with illustrations for this method.

Once you have the calculations made, store them somewhere safe for the next time you need them, or for the next person who owns your house. If someone had done that for us, it would have saved a lot of time and trouble.