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Measuring for your Skylight

Size is typically the most important factor in purchasing and installing a skylight. While both size and position will determine how much extra light is admitted to the space below, size is the dominant factor. Use the following "rule of thumb" for sizing a skylight: the skylight size should never be more than 5% of the floor area in rooms with many windows and no more than 15% of the room's total floor area for spaces with few windows.

Keep in mind that the measure is absolutely critical! It must be accurate and needs to be based upon typical industry reference points as provided below. Nothing can be more frustrating than receiving the wrong sized material. Although it is nothing to be afraid of, we would encourage you to familiarize yourself so as to avoid a potentially costly mistake.

When ordering or describing a skylight, the measurements are always expressed as width (dimension horizontally across the roof) x length (dimension vertically up the roof).On venting skylights, the hinge will be on the width dimension.

Thermo-Lite series skylights are fitted into an opening in the roof. The 'rough opening' is the size of the hole built into or cut into the roof to accept the skylight. The actual size of the skylight will be 1/2" smaller in both width and length, allowing some ability to adjust the actual skylight position within that opening.

Metro-Lite series skylights are mounted onto curbs on the roof. Curb Mounted frame sizing is taken from the Outside Curb Dimension. The Outside Curb Dimension is the overall OD (outside dimension) size of the of the finished built up curb. Importantly, this also includes the applied roofing materials as taken from the top of the curb where the skylight is to fit. Skylights are sized slightly larger than the OD of the curb in order to fit over the top like a crown, and reference what is commonly referred to as  the Inside Flange Dimension, also known as the Inside Aluminum Dimension or the Inside Unit Dimension. The important issue here is that you provide us with the proper OD of the curb. We can assist you with the rest!

Venting Glass Fixed Glass
Rough Opening
(Width x Height)
CGV1430 CGF1430 14½" x 30½"
CGV1445 CGF1445 14½" x 45½"
CGV1460 CGF1460 14½" x 60½"
CGV2222 CGF2222 22½" x 22½"
CGV2230 CGF2230 22½" x 30½"
CGV2245 CGF2245 22½" x 45½"
CGV2260 CGF2260 22½" x 60½"
CGV2272 CGF2272 22½" x 72½"
CGV3030 CGF3030 30½" x 30½"
CGV3045 CGF3045 30½" x 45½"
CGV3060 CGF3060 30½" x 60½"
CGV3072 CGF3072 30½" x 72½"
CGV4545 CGF4545 45½" x 45½"



Fixed Acrylic Venting Acrylic Venting Glass
Outside Curb Dimension
(Width x Height)
CMA2525 CVA2525 CVG2525 25½" x 25½"
CMA2533 CVA2533 CVG2533 25½" x 33½"
CMA2537 CVA2537 CVG2537 25½" x 37½"
CMA2549 CVA2549 CVG2549 25½" x 49½"
CMA3333 CVA3333 CVG3333 33½" x 33½"
CMA3725 CVA3725 CVG3725 37½" x 25½"
CMA3737 CVA3737 CVG3737 37½" x 37½"
CMA3749 CVA3749 CVG3749 37½" x 49½"
CMA4933 CVA4933 CVG4933 49½" x 33½"
CMA4949 CVA4949 CVG4949 49½" x 49½"

Should you need a skylight size that is not included in the size charts above, don't worry: both the Thermo-Lite and Metro-Lite series skylights can be ordered in custom sizes. Please use our Custom Sizes page to request a quote for your custom size skylight..

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