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Number of Shingle Courses for Roofing Contractor License

To calculate the number of shingle course on a roof, follow the formula below:

Number of Courses = Width of Roof Section (eave to ridge along common rafter)/Exposure

Example: Calculate the number of courses of 12-inch-wide asphalt shingles required to cover the roof below. Assume a slope of 6 in 12 and 5-inch exposure.


On the roof plan, the distance from the eave to the ridge is 20’. We use the table below to identify the actual distance


  • The common/jack factor for 6 in 12 slope is 1.118.
  • 20’ x 1.118 = 22.36' actual length
  • Number of courses = 22.36' / 5"

Note: before dividing, we must standardize our units. They must be both inches or feet. Let’s multiply the numerator (22.36’) times 12 to convert it to inches.

22.36 x 12 / 5 = 53.66 or 54 Courses.

This means that one of the two sections of the roof has 54 courses since the other section is exactly the same, we simply multiply times 2 to get the total number of courses. 54 x 2 = 108

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