As a general rule, calculate the area of one skylight as follows, where SRR is the skylight-to-roof ratio:
(Floor to Ceiling Height x 1.5)² x SRR
Choose a size that is appropriate for the project. Starting with 5% SRR, modify this value depending on climate and building use.
For example, with a 12-foot ceiling and 5% SRR, the correct size for a skylight is approximately (12 x 1.5)² x 5% = 16.2 square feet. Therefore, the project should use 4' x 4' skylights.