Standard Skylight Sizes

Skylights are excellent fixtures to add light to rooms with no windows, increase light in dimly lit rooms or add dramatic lighting effects to large open spaces. They can be incorporated into the designs for newly constructed homes or installed in older ones. Skylights come in various shapes and sizes to provide different levels of illumination in rooms of various dimensions.

Sizes and Shapes

Skylights come in various shapes and sizes.

The standard sizes of skylight range from 14 square inches to 4 square feet, although larger sizes are available for large commercial buildings. Rectangular-shaped skylights typically chosen for sloped roofs can be as long as 8 feet. Some square skylights are installed in clusters of small sizes to illuminate rooms with angled beams of light. If you want an oddly shaped or oversized skylight, it can be custom made by skylight manufacturers.


The two main types of skylights are stationary or fixed, and operable or ventilating. Stationary skylights are comparable to fixed windows that cannot be opened or closed and are commonly dome-shaped or flat. Operable models are opened and closed by hand cranks, electrical wall switches, remote control pads or temperature sensors. Ventilating models are practical for bathrooms to let steamy shower or bath water escape or for larger hot rooms where they suck the hot air near the ceiling out of the room and leave the cooler air near the floor. Bathrooms that are too small for standard skylights often have tubular types made from a 10 to 18 inch wide tube with a clear dome attached to a reflective pipe that diffuses the light and illuminates the entire room.


Traditional skylights of years past offered no glass options; they were single-pane glass with a window frame around them. To keep heat absorption and UV rays in check, modern skylights have glass options that include tinted and protective coatings. Shades or blinds are alternatives to tinted glass, which reduce the brightness of natural light. Operable skylights can be installed with screens to keep out insects and debris.

Measuring for Skylights

To determine what size skylight is best for your room, the industry has a formula for homeowners to follow. For rooms with many windows, the skylight size should be 5 percent or less of the floor area. If the room has a minimal number of windows or very small ones, the skylight should be no larger than 15 percent of the floor area.

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