Quick reference
What size lite fits this door?
It varies — by leaf construction, by door width, by the hardware going in, and by whether the opening is rated. Here is the part that can be answered in advance, drawn to scale, so you know before you draw it.
A planning guide, not an approval. Everything here is the border a leaf typically needs and the reasoning behind it. The final size on any opening is the manufacturer’s to approve, and we always defer to their current documentation at drawing approval — including on anything rated, where the glazed area is set by that specific door’s listing rather than by any general rule. Use this to plan; let us confirm it before it is drawn.
Lite sizing tool
Pick the leaf. See what it takes.
Change the door and the drawing changes with it. The dashed outline is the largest cutout that leaf will accept once the solid border is held; the shaded panel is the glass you picked.
Drawn to scale · 3'0" × 6'8" leaf
Fits typical margins
- Largest cutout this leaf takes
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- Your glass size
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- Solid border held
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Rated leaf — one more step. The border above is geometry. On a rated opening the glazed area also has to sit inside that specific door's listing, which is the manufacturer's to state and ours to get for you. Send us the opening and we will confirm it against the current document before anything is drawn.
Why the answer moves
Four things decide it.
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How wide the leaf is
The border is fixed, so every inch of door width you lose comes straight off the glass — twice, once at each edge. This is why a lite that is routine on a 3′0" door is impossible on a 2′8" one.
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What the hardware needs
A lock case needs a solid stile to sit in, and an exit device needs more room than a plain lockset. The lock edge is almost always the tighter of the two vertical borders, and it is the one people forget.
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Whether the opening is rated
A rated leaf is a tested assembly. The glazed area it will carry is stated in that specific door’s listing, and it is normally well inside what the leaf could take structurally. This is the single biggest reason a size that looks fine on paper comes back rejected.
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What else is in the leaf
A louver, a second lite, or a wide bottom rail for a sweep all compete for the same slab. Two cutouts in one leaf also need a solid buffer between them, which is easy to miss until the shop drawing comes back.
Reference
The solid border, by leaf type.
Typical minimums. Individual manufacturers publish their own and some differ — where a job is tight, we will pull the figure for the door you are actually buying.
Architectural wood — flush, solid core
A flush wood leaf carries its strength in the stiles and rails around the core. Cut into that band and the leaf loses the material the hinges screw into and the lock case sits in, so the border stays solid.
| Hinge edge | 5″ |
|---|---|
| Lock edge | 5″ |
| Clear of the lock prep | 5″ |
| Top rail | 5″ |
| Bottom rail | 10″ |
| Between two lites | 3″ |
Commercial hollow metal — steel
A hollow-metal leaf is a steel skin over internal channels and reinforcements. The border has to clear those channels — which is why the numbers run an inch or so wider than wood, and why the bottom needs room for the bottom channel.
| Hinge edge | 6″ |
|---|---|
| Lock edge | 6″ |
| Clear of the lock prep | 6″ |
| Top rail | 6″ |
| Bottom rail | 10″ |
| Between two lites | 5″ |
One more to keep in view: where a lite exists so people can actually see through it, barrier-free requirements set a maximum height for the bottom edge of the glass. It rarely bites on a normal lite, but it does on a small high viewport — worth checking early rather than at approval.
Before anyone reaches for a saw
Order it prepped. Do not cut it on site.
A rated door is a tested assembly, and the label belongs to the door as it was built. Cutting a lite or a louver opening into a rated leaf in the field voids that label — and it is discovered at inspection, after the opening is hung and the schedule has no room left.
Glazed openings in a rated leaf have to be prepped at the factory, or by a shop carrying a certified label service that can re-label the door afterwards. There is no version of this that a jobsite jigsaw or a torch makes acceptable, and filling an unwanted hole with body filler or wood putty is not a repair either.
Some small preparations are permitted in the field and some are categorically not, and the line between them is narrower than most people assume. If a change is needed after the door is on site, ask before it is made — that call takes a minute and it is considerably cheaper than a replacement leaf.
The lines behind a glazed opening
Every part of a glazed opening, one call.
A lite is not one product. The leaf, the frame that finishes the cutout and the glass inside it are separate listings from separate factories — which is precisely where openings come apart. Each of these is a line we partner with, and their current documentation is the authority on sizing.
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The wood leaf
Lambton Door
Architectural wood doors. The core construction decides what the leaf will take, so their cutout limits are the ones that govern a wood opening.
Manufacturer documentation (opens manufacturer site in a new tab)
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The steel leaf
DeLa Fontaine
Hollow metal doors and frames. Where the internal channels and reinforcements sit is what decides the border on a steel leaf.
Manufacturer documentation (opens manufacturer site in a new tab)
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The lite frame
Anemostat
Vision frames, lite kits and door louvers — the frame that finishes the cutout and holds the glass, in standard, security and rated versions.
Manufacturer documentation (opens manufacturer site in a new tab)
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The glass
Glassopolis
Architectural glazing for door lites, including rated and impact-safe products. What goes in the frame is its own listing, separate from the door.
Manufacturer documentation (opens manufacturer site in a new tab)
Send us the opening and we will confirm the lite before it is drawn.
Tell us the leaf, the hardware and whether it is rated. We will come back with what that manufacturer will actually cut, from their current documentation — not a general rule.