Things You'll Need
2-foot carpenter's level
Roof pitch is defined as the slope of the roof and is stated as the amount the roof drops for each horizontal 1-foot distance of the roof. The higher the number of the pitch, the steeper the roof. A 12-inch pitch or slope rises 1 foot for every 1 foot of horizontal distance. This is the equivalent of a 45-degree angle. Most roofs have a much shallower pitch, 3 or 4 pitches the most common, indicating a rise in the roof of 3 or 4 inches for each horizontal foot. Calculating the pitch requires a couple of basic carpentry tools and just a few minutes of time.
Place one end of a 2-foot carpenter's level on the roof at least 2 feet from the eaves. Raise the other end of the level until the bubble indicates the level is being held level.
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Measure the distance between the elevated end of the level and the roof directly below. State the measurement in inches. This is the pitch of a 2-foot section of the roof.
Divide the measurement by 2 to calculate the pitch of the roof per foot. Divide the 1-foot roof pitch by 12 to determine the slope of the roof in degrees.
A 4-foot level can be used in the same manner. Divide the distance by 4 rather than 2 to calculate pitch of the roof per foot.
Calculating the pitch of a roof this way requires working on the roof. Use the standard safety precautions for working on a ladder or roof to prevent falls.