Sloped Roof Pitch Conversion

Correct horizontally measured roof area to its actual pitched area where pitch is defined as rise over run. Horizontal measurement (2D measurement) is typical when a pitched roof is measured from ground level, blueprint or aerial photograph.

1:12 = 1.00
2:12 = 1.01
3:12 = 1.03
4:12 = 1.05
5:12 = 1.08
6:12 = 1.12
7:12 = 1.16
8:12 = 1.20
9:12 = 1.25
10:12 = 1.30
11:12 = 1.36
12:12 = 1.41

Example: given a 4:12 pitch and 10,000 square feet measured horizontally.

• True roof area = 10,000 square feet * 1.05 = 10,500 square feet = 105 squares

1 roofing square = 100 square feet