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.
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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.
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.