VELUX Skylight:
This covers almost any VELUX Skylight from the last thirty years. This calculator requires measuring the outside visible exterior glass dimensions of the existing skylight on the roof.

Stepped Flashed / Self Flashed Skylight:
Non-VELUX / Other
This skylight is mounted directly onto the roof deck and usually has a factory step flashing kit with it. This calculator requires measuring the inside finished drywall dimensions of the existing skylight.

Curb Mount Skylight:
This skylight is mounted onto a flashed, site-built curb and fastened into place. This calculator requires measuring the outside base curb dimensions (including flashing) of the existing skylight curb on the roof.