Window screens are one of the few things in a house that are built to your measurements, not pulled off a shelf. That is good news — it means a screen can fit an eighty-year-old Glendora casement as neatly as it fits a brand-new slider. It is also why a quarter-inch mistake turns into a screen that rattles in the wind, pops out of the track, or won’t go in at all.
We build screens in our La Verne shop for homes across Glendora, La Verne, San Dimas, Claremont, Covina, Azusa, Pomona, and Upland, and we have been doing it since 1989 — 36 years, family owned. In that time we have learned that when a screen doesn’t fit, it is almost never the shop’s math. It is one of five predictable measuring mistakes. Here is how to measure window screens the way we do, and how to avoid every one of them.
The short version
If you still have the old screen, measure that — outside edge to outside edge of the aluminum frame, plus the frame thickness. If the old screen is long gone, you are measuring the opening instead, and the rules change. Both are below. Either way, you can always text us a photo and skip the tape measure.
Step 1: figure out which kind of screen you have
Before you measure window screens you need to know how they mount, because that determines what you measure and what clearance we build in. Nearly every screen in the San Gabriel Valley falls into one of four families.
Full-frame screens with spring plungers
The screen sits inside the window opening and is held by two spring-loaded pins on one side. Push the pins in, the screen drops out. These are common on aluminum casements and older awning windows — and very common in the older homes around Glendora’s foothill streets.
Half screens for sliders and single-hung windows
These cover only half the opening and ride in a shallow track. Horizontal sliders (the most common window in mid-century SoCal tracts) take a vertical half screen; single-hung windows take a horizontal one. If you are not sure which style you have, our window styles guide sorts it out in about a minute.
Tension-clip and pull-tab screens
Newer vinyl and retrofit windows often use flexible clips or a small pull tab instead of plungers. These need a snug friction fit, so the tolerances are tighter and the frame thickness matters more.
Door screens and sliding screen doors
Different animal entirely — they roll on wheels in a track and have to be measured for height with the roller adjustment in mind. If your screen door is dragging rather than torn, read the roller repair walkthrough before you measure for a new one.
Take a picture before you take it apart
Photograph the screen in the opening, then the corner hardware, then the side of the frame. Those three photos answer most of the questions we would otherwise have to call you about.
Step 2: how to measure window screens you still have
This is the easy case, and it is the one we want. An existing screen already contains every clearance decision the last builder made. Copy it.
- Take the screen out and lay it flat. On a table or the driveway — not leaning against the wall, where the frame can flex.
- Measure the frame, not the mesh. Outside edge to outside edge of the aluminum, both directions. The mesh is inset from the frame edge and measuring to it will cost you roughly a half inch in each direction.
- Work in sixteenths. Screens are cut to the sixteenth. “About thirty-two and a half” becomes a screen that rattles. Write down 32 7/16 if that is what it says.
- Measure the frame thickness. This is the number people forget. Residential screen frame stock is commonly 5/16″, 7/16″, or 3/4″ deep, and the wrong depth won’t seat in the track even when width and height are perfect. Measure the side of the frame, not the face.
- Note the frame profile and corner type. Flat frame or lipped? Square corners or a rounded corner key? Mitered or straight-cut? A quick photo covers all of it.
- Note the hardware and which side it is on. Plungers, clips, pull tabs, finger holes — and whether they sit left, right, top, or bottom as the screen faces you from outside.
- Label every screen. Masking tape on the frame: “kitchen north,” “back bedroom.” Windows that look identical rarely are, especially in houses that have been re-stuccoed or had a window swapped over the years.
Step 3: what to do when the old screen is gone
Missing screens are the norm, not the exception. They blow off during Santa Ana wind events, get thrown out during a paint job, or simply never came with the house. Now you are measuring the opening, and there is a clearance allowance involved — the screen has to be smaller than the hole it lives in, but not so much smaller that it falls out.
Measure the opening in three places across and three places up and down, then record the smallest of each. Openings are rarely square, particularly in older stucco homes. Also record the depth of the channel or the height of the retaining lip, because that is what tells us how much of a bite the frame has to take.
Then — and we mean this — tell us those are opening measurements, not frame measurements. We will take the clearance off in the shop. If you subtract it yourself and we subtract it again, you get a screen that whistles.
The single most common bad measurement we receive: an opening measurement handed to us as if it were a frame measurement.
What to measure, by screen type
| Screen type | Measure | Also record | Common gotcha |
|---|---|---|---|
| Full frame, spring plungers | Old frame, outside to outside | Plunger side; frame depth | Plungers add length — measure the frame, not pin tip to pin tip |
| Slider half screen | Old frame, outside to outside | Track depth; which half it covers | Left and right halves are often different widths |
| Single-hung half screen | Old frame, outside to outside | Whether it sits inside or on a lip | Upper and lower sash openings are not the same |
| Tension clip / pull tab | Old frame, outside to outside | Clip locations; frame depth | Friction fit — sixteenths matter more here than anywhere |
| Sliding screen door | Track to track, floor to header | Roller type; door handle side | Roller adjustment changes effective height by up to an inch |
The five mistakes that cause a second trip
- Measuring the mesh instead of the frame. The number one cause of undersized screens, every year.
- Rounding to the nearest half inch. Screen work lives in sixteenths. Rounding is how a screen ends up loose enough for the first real wind to take it.
- Skipping the frame thickness. Perfect width, perfect height, wrong depth — and it will not seat in the track. This one is invisible until installation day.
- Assuming matching windows are matching sizes. Two windows on the same wall, installed the same week, can differ by three-eighths. Measure each one.
- Measuring over the stucco or the paint build-up. Measure the actual opening or the actual channel, not the finish that has grown into it over 40 years.
While you have it out: decide on the mesh
A new frame is the right time to change what is stretched across it, because the labor is the same either way. The default charcoal fiberglass is fine for most windows, but it is not the only choice, and it is often not the best one for a specific opening.
- Solar mesh blocks a meaningful share of the heat before it reaches the glass — worth it on west and south exposures, and one of the cheaper moves in our keep-the-house-cool guide.
- Pet mesh is several times tougher than standard fiberglass. If a dog or cat has already been through one screen, see how pet screens hold up.
- Security screens are a different product with a steel frame and a locking system, not a mesh swap — we cover whether they’re worth it separately.
- Tighter no-see-um weaves for anyone near open space or a creek bed.
The full rundown, side by side, is in our mesh comparison. And if the frame itself is straight and the corners are tight, you may not need a new frame at all — re-screening the one you have is usually the cheaper, faster call.
When to skip all of this and let us measure
Measuring is genuinely not hard, and plenty of our customers do it well. But there are four situations where we would rather come out with our own tape:
- More than about six screens. The chance of one transcription error approaches certainty, and one wrong screen means a return trip anyway.
- No original screens anywhere on the house. With nothing to copy, the clearance call is a judgment call, and it is ours to get wrong.
- Second-story or hard-to-reach openings. Not worth a ladder for a measurement.
- The window itself is the problem. If a sash is stuck, binding, or out of square, a new screen won’t fix what you’re actually noticing — and a square screen in an out-of-square opening never looks right. That’s a window repair conversation first.
Estimates are free, and we cover Glendora and the surrounding cities out of the La Verne shop.
Fastest option, honestly
Text a photo of the screen and the window to (626) 335-2900. Nine times out of ten we can tell you the screen type, the likely frame stock, and whether you need a re-screen or a new frame before anybody measures anything. We don’t publish a flat per-screen price because size, mesh, and frame stock all move it — but we’ll quote you a real number, not a range that changes at the door.
Quick answers
Do I measure window screens from inside or outside the house?
Measure the screen frame itself, lying flat, so the question doesn’t arise. If you’re measuring an opening because the screen is missing, measure from outside — that’s the face the screen mounts to — and note which side the hardware needs to be on as you look at the window from the yard.
How much smaller than the opening should a window screen be?
That depends entirely on the mount — a plunger screen, a track-riding half screen, and a tension-clip screen each need a different allowance. Give us the opening measurement and tell us it’s an opening measurement; we take the clearance off in the shop.
Can you match a screen frame color?
Usually. Screen frame stock comes in a handful of standard finishes — mill, white, bronze, and black are the common ones — and we can generally match what’s already on the house. Bring one old screen in, or send a photo.
The bottom line
Measure the frame, not the mesh. Work in sixteenths. Write down the frame thickness. Label everything. Do those four things and the screens we build will drop into your openings like they were always there.
And if you’d rather not: that’s what we’re for. Glendora Window has been building screens for San Gabriel Valley homes since 1989 — 4.8 stars across 160+ verified reviews, 50,000+ jobs completed. Bring your screens by the shop at 1782 N White Ave in La Verne, or request a free estimate and we’ll come measure them ourselves.
