How to find a roof pitch using an angle finder

Updated February 21, 2017

Finding the correct pitch of a roof is very important when planning for roofing repairs or remodelling. Roof pitches and angles need to be cut properly in order for the roof to be structurally sound and support the weight of the roof and everything that comes in contact with the roof. Using an angle finder is the easiest and most accurate way to determine the correct pitch of the roof. An angle finder looks like an adjustable square where the middle is pinned to allow the arms to make any angle. Think of a ruler that has a pin in the middle and can spin on that pin 180 degrees.

Set up the extension ladder at the eave of the house. Make sure the ladder rests on stable, level ground and is angled slightly to avoid tipping.

Taking the level and angle finder with you, climb up the ladder onto the roof and then up to the peak. Walking at an angle on the roof will make it easier to walk to the peak and create less wear and tear on the shingles.

Avoid walking on clay, tile or slate roofs. Instead, set the ladder at the end wall of the house and extend the ladder to the peak, working solely from the ladder.

Place one side of the bottom of the level on the roof peak while the other is supported in your hand. Only one end of the level should be on the roof peak. Use the indicator bubble on the level to make the level horizontal with the ground. The bubble should be in between the lines on the indicator glass.

Place one edge of the angle finder on the roof surface below the level, and the other edge on the bottom of the level while maintaining a horizontal plain with the ground. Double check your angle before leaving the roof. Some more advanced angle finders have a gauge the indicates the exact degree of the angle for the roof pitch. For cutting purposes, all you need is the angle and the ability to transfer this angle to structural members.


The angle finder can also be used to find odd angles when working with drywall, decorative trim, and furniture. Angle finders come in a wide variety of sizes. The larger the angle finder, generally, the greater its accuracy for applications such as roof pitch.


Always use caution when walking on a roof. Never walk on tile, slate, or clay roofs or when the roof surface is wet or covered with snow.

Things You'll Need

  • Extension ladder
  • Level
  • Angle finder
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About the Author

Adam Yeomans has been writing professionally since 2010, with his work appearing on websites such as eHow. He works in the construction industry as a builder and as an energy efficiency consultant.