The only hard width number in the research is New York's 20 in exemption threshold; everything else depends on the opening and the product sizes you choose.
Standing at the front door with a tape measure, it's easy to worry that adding narrow glass panels beside the door will squeeze the entry or look out of proportion. When they're sized well, those panels can brighten a dark foyer and make a standard door feel larger without changing the door itself. You'll get a clear path to pick a width that meets rules, fits the opening, and delivers the look you want.
Minimum width in code: the trigger, not the target
New York's transparent-glass sidelight rule exempts panels 20 in wide or less when they have opaque stiles at least 1.75 in, and it also removes panels from scope when a permanent barrier blocks approach or when an opaque sill and wall are at least 18 in high. So a 19 in wide panel with 2 in stiles beside a lobby door can fall under the exemption, while a 22 in panel in the same spot stays in scope and should be designed for compliance.
ADA guidance on door clear width and maneuvering clearances stays focused on the door opening, not the sidelight, so adding glass beside the door does not change accessibility unless the opening changes. On a renovation, you can add a sidelight to gain visibility to the porch, but the usable opening remains what it was.
Measure the opening first, then size the sidelights
Measure jamb-to-jamb at multiple points because sidelights are narrow windows on one or both sides of a front door and the total width must fit the opening. If your smallest jamb-to-jamb measurement is 61.75 in, that number controls the combined door-and-sidelight width even if the top reads wider, which keeps the unit from binding later.
For full-unit replacements, prehung systems are ordered about 1 to 1.5 in smaller than the rough opening, which leaves room for shims and adjustment. A 66 in rough opening points to a unit around 64.5 to 65 in. If the existing frame is damaged or leaking, an integrated, factory-joined unit is usually the cleanest reset, while glass-only replacement is reserved for sound frames with broken or fogged panels.
What "minimum" looks like in the real marketplace
Many homeowners encounter width limits through product availability, because standard call sizes dominate sidelight inserts. Common options include 7x64, 8x36, 20x64, and 22x64 in, which means a 7x64 reads as a slim accent while a 22x64 creates a stronger glass field; if your opening matches a stock size, you can often avoid custom fabrication.
Call size (in) |
7x64 |
8x36 |
20x36 |
22x36 |
20x64 |
22x64 |
On replacements, I record tip-to-tip size, glass size, glass thickness, and cut-out size because the surround will not fit if those don't match, and insulated glass is typically 1/2 in or 1 in thick. When reusing existing glass, I confirm thickness before ordering a new rim so the cut-out stays true, since the cut-out is usually 1 to 1.25 in larger than the glass size.
Width choices and the curb-appeal payoff
Full-length sidelights admit more light than door glass and make a standard door feel larger, so the visual payoff often shows up even when width is modest. In a shaded entry, adding sidelights that match the door height can lift the brightness of the foyer without reworking the door itself.
Clear glass maximizes light while frosted, etched, or decorative glass preserves privacy, and tempered or impact-resistant options add security. Insulated or Low-E glass helps control heat gain or loss as the glass area grows. If the entry faces a sidewalk, a patterned panel keeps daylight while blurring views, and in storm-prone areas, impact-resistant glass keeps the same width but raises resilience.
Choose the width that the opening truly allows, check local rules when the glass is public-facing, and let glass type handle privacy and security. Done right, a sidelight package reads intentional, bright, and built to last.
