Double-hung windows are the most common window style in American homes, but they are also the one most people measure incorrectly for screens. The reason is simple: a double-hung window has two sashes, and the screen does not cover the whole window — it covers only the lower half where the bottom sash slides up.

If you measure the full window opening, the screen will be too tall. If you measure the glass instead of the screen channel, it will be too narrow. This guide walks through the correct process for measuring a double-hung window for a custom screen, based on standard American window construction and screen replacement practices.

What Makes Double-Hung Windows Different A double-hung window has two vertically sliding sashes. The screen sits in a channel or track on the exterior (or sometimes interior) of the lower opening. When the bottom sash is raised, the screen is what keeps insects out of the open space.

This means the measurement you need is not the window’s overall size. It is the screen opening — the precise channel or track where the screen frame sits. According to screen manufacturers, measuring the existing screen frame (if it fits well) is the most reliable method, but if the old screen is warped or missing, you must measure the window opening directly .

Tools You Need You do not need special equipment. A standard metal tape measure with 1/16-inch markings is sufficient. Avoid cloth tapes — they stretch, and a 1/8-inch error is enough to make a screen bind or fall out .

You also need a pen and paper to record each measurement. Label each window clearly (e.g., “Bedroom North – Window 1”) so you do not mix up sizes when ordering.

Step-by-Step: Measuring for a Double-Hung Screen Step 1: Remove the old screen (if possible) If an existing screen is in place, remove it carefully. Do not measure the old screen unless it fits perfectly — old screens warp, and copying a warped screen gives you a warped replacement . If the old screen is in good condition and fits well, you can measure its outside frame dimensions as a reference, but the window opening is the primary source of truth.

Step 2: Measure the width of the screen opening Open the bottom sash fully so you have clear access to the screen channel.

Measure from the inside lip of the left screen channel to the inside lip of the right screen channel. This is the width where the screen frame will sit.

Take this measurement at three points: near the top of the channel, in the middle, and near the bottom. Window frames settle and are rarely perfectly square. Record all three measurements and use the smallest one. This ensures the screen will fit even if the opening is slightly irregular .

Step 3: Measure the height of the screen opening Measure from the top of the screen channel (where the top of the screen frame seats) to the bottom of the channel (the sill or the bottom stop where the screen rests).

Again, measure at three points: left side, center, and right side. Use the smallest measurement.

Critical note: For double-hung windows, the screen height is usually not the full window height. It is the height of the lower opening only — the area that is exposed when the bottom sash is raised. If you measure the full window height, the screen will be far too tall.

Step 4: Check the frame depth Double-hung screens sit in a channel or track. Measure the depth of that channel from front to back. This typically runs between 3/4 inch and 1 inch, but it varies by window manufacturer . If your window has an unusual channel depth, note it and mention it when ordering — the screen frame thickness must match the channel.

Step 5: Note any hardware Look for springs, clips, tabs, or latches in the channel. Double-hung screens often use spring-loaded pins or wing blades to hold the screen in place . These hardware components take up space, and a screen that is too tight will not compress the springs enough to seat. Note their location and type, and include this information in your order.

Step 6: Photograph the measurement Place the tape measure against the channel and photograph it with the numbers clearly visible. Do this for both width and height. This photo is your proof if there is any question about the measurement later. It also helps our team confirm the fit before production.

The Mistakes That Cause Most Double-Hung Screen Problems Measuring the glass instead of the channel The screen does not sit on the glass. It sits in the channel around the opening. Measuring the visible glass gives you a screen that is too small.

Measuring the full window height A double-hung screen covers only the lower opening. Measuring the full window height (from head to sill) gives you a screen that will not fit.

Measuring only one point Window frames are rarely perfectly square. If you measure only the middle and the opening is narrower at the bottom, the screen will bind. Measure at three points and use the smallest.

Rounding to the nearest inch Screen frames are cut to 1/16-inch tolerances. Rounding to the nearest inch (or even 1/8 inch) can create a gap or a bind. Record the exact measurement, even if it looks awkward (e.g., 31 7/16 inches, not 31.5) .

Ignoring the hardware If your window has spring pins and you do not account for them, the screen may not seat properly. Mention the hardware when ordering.

What to Send Us When you are ready to order a custom screen for your double-hung window, send us:

Width — exact measurement to the nearest 1/16 inch (the smallest of the three width readings)

Height — exact measurement to the nearest 1/16 inch (the smallest of the three height readings)

Channel depth — front-to-back measurement of the screen track

Photos — showing the tape measure in the channel for both width and height

Hardware notes — springs, clips, tabs, or latches and their locations

Frame color preference — if you want the screen frame to match your window frame

We will confirm the fit before production and send a free quote within 24 hours. If the measurement is wrong on our side, we remake the screen at no cost.

A Quick Reference for American Double-Hung Windows While there is no universal “standard” screen size, many American double-hung windows fall within common ranges. A 36-inch by 48-inch window (often called a 3040) is one of the most common sizes, but screens for these windows are cut to the specific channel, not the nominal window size . Custom measurement is always required.

If you are unsure whether your window is a double-hung or single-hung, check whether both sashes move. If only the bottom sash moves and the top is fixed, it is single-hung — the screen measurement process is similar, but the screen is often fixed in the lower section rather than removable.

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