In this blog:
- Window sizes generally follow a four-digit numbering system. To leave room for installation, the actual window is usually about ½ in. smaller than its stated size.
- Standard window sizes vary depending on the window style. Each style has common size ranges, but they can vary considerably.
- Measuring correctly helps determine whether a standard window will fit your space. Window World includes professional measurements as part of its free in-home estimate.
Replacement windows come in a lot of different sizes, and if you’re on the hunt for a new set for your New Orleans home, you’re probably wondering what you need to look for to find the perfect fit. The good news is, window sizing is actually easier than it might first appear.
Most residential windows fall within a set of standard size ranges that are typically widely available. Those size ranges vary depending on the type of window. Below, we’ve broken down the most common window sizes by window type, explained how to read them and shown you how to measure an existing window opening. Let’s dive in.
How Window Sizes Are Written and Measured
Window manufacturers frequently follow a standardized four-digit numbering code when sizing replacement windows. The first two digits typically represent the window’s width, while the last two represent the height. Each pair of numbers shows the feet and inches of the window’s dimensions.
For example:
- A 3020 window measures 3 ft. 0 in. wide x 2 ft. 0 in. tall.
- A 2846 window measures 2 ft. 8 in. wide x 4 ft. 6 in. tall.
Keep in mind, while these numbers are close estimates, they are likely only a window’s nominal size. Nominal sizes are just a generalized measurement that window manufacturers use when labeling their window sizes. Most manufacturers make their windows’ exact heights and widths about ½ in. or so smaller. Therefore, the 3020 window above may actually measure 35 ½ in. x 23 ½ in if you take a tape measure to it.
The reason for this slight discrepancy is that it allows the necessary space that you’ll need for positioning, caulking, shims, insulation and flashing when you install the window in your wall. The hole in your wall is called a rough opening, and you’ll always want to measure it before selecting a window size. If you have a 3 ft. x 2 ft. rough opening, the 3020 window may provide the snug, insulated fit you need.
Standard Window Sizes by Window Type
Window size options will vary depending on the window style in question, and windows may differ slightly in size between manufacturers. Use this standard window size chart as a reference:
| Window Type | Common Width by Height Range |
| Double-hung | 24–48 in. wide x 36–72 in. tall |
| Sliding | 36–84 in. wide x 24–60 in. tall |
| Casement | 16–48 in. wide x 24–84 in. tall |
| Awning (typically wider than tall) | 16–48 in. wide x 24–84 in. tall |
| Picture (fixed) | 34–72 in. wide x 36–60 in. tall |
| Bay or bow (by full assembly) | 42–126 in. wide x 36–78 in. tall |
A few of the more common residential window sizes include:
- 24 x 36 in.
- 30 x 40 in.
- 32 x 52 in.
- 36 x 60 in.
What’s important to remember, however, is that all rough openings for windows vary. Even two near-identical windows sitting side by side in the same home might vary enough to require separate window sizes. Code may also require you to install certain-sized windows, such as egress windows, in certain areas.
A Note on Egress Windows
Egress windows are windows that make it easier for residents to escape or for first responders to enter in an emergency. Egress windows must meet certain sizing criteria to allow people to pass through them. Various window styles may qualify as egress windows if they are the right size.
Most homes are required by code to have at least one egress window installed in certain rooms. You’ll often have to put them in bedrooms, and if your Louisiana home happens to have a finished basement, you may have to have an egress window there, too.
Many building codes, including the Louisiana State Universal Construction Code, base their egress window sizing requirements on International Residential Code standards. Under the code:
- Egress windows generally need a net clear opening area of at least 5.7 sq. ft.
- The opening must be at least 20 in. wide and 24 in. high.
- The opening cannot be more than 44 in. above the floor.
However, keep in mind that local construction codes can vary widely. Always confirm egress window requirements with your local permitting authority or an experienced window installer.
How to Measure Your Windows for Replacement
Before you begin shopping for windows, it helps to take a few preliminary measurements to decide the size you might need.
Keep in mind, many modern windows, including Window World’s, come with the full window apparatus, including the frame and other structural components. They will then be fitted into your rough opening. Therefore, you’ll want to measure the window structure, not just the glass.
Here’s how to measure:
- Measure the window’s width. Measure the window’s width at the top, middle and bottom. Then, record the smallest number, rounding down to the nearest ⅛ in.
- Measure the height. Take three measurements of the height from the left, center and right of the window. Record the smallest number, again rounding down to the nearest ⅛ in.
- Measure clearance. If you’re buying a window that opens or protrudes outward, such as awning, casement or bay windows, you may need to measure the exterior clearance. You’ll need a good idea of how much space you need for your windows.
Because window measurements can get complicated, we highly recommend having your windows professionally measured. Your Window World representative will gladly take full measurements at the time we complete your free in-home window assessment.
Standard Size or Custom Window: Which Do You Need?
Many modern homes are built with standard window sizes in mind, so if you’re shopping for windows, you’ll likely find it easy to get a size that fits. However, this isn’t always the case.
Older homes, homes with alterations or those with nonstandard framing may require you to have custom windows designed. That’s why it’s so important to have a professional measure your windows before you move to installation. Don’t try to fit a window where it won’t go. If you do, you risk damaging the home’s structure, moisture intrusion and drafts that could affect your home’s energy efficiency.
Why Window Size Affects Energy Efficiency and Curb Appeal
Having the right-sized window in the right place ensures your home is sealed, secure and looks its best. Improperly fitted windows might:
- Cause your home’s energy efficiency to drop. Windows with gaps around the frame can allow drafts and moisture into your home, draw comfortable air out and force your HVAC systems to work harder. Your utility costs may rise as a result.
- Put your home at risk of structural damage, especially if you try to force a window that is too large into a smaller space.
- Affect your home’s safety. Windows that don’t fit may not lock as securely, and they may be easier to open from the outside.
The correct window proportions can also do a lot to improve your home’s aesthetic. Windows help your home appear balanced, angular and proportional, and even small inconsistencies can throw that balance off.
Not Sure What Window Size You Need? We’ll Measure It.
You don’t have to be an expert measurer to choose the correct window size. Just leave it to the experts at Window World. As part of your free in-home estimate, we’ll professionally measure all aspects of your window to determine whether a standard or custom size is best. We will then expertly install your window to ensure it is perfectly balanced, sealed and set to provide optimal protection and great views well into the future.
So, why struggle with the guesswork? Trust your Louisiana home’s new windows to Window World of New Orleans. Get a free quote today, and let us take care of the hard work.
Frequently Asked Questions
What is the most common window size for a house?
Window sizes vary from home to home, so there’s no real most common size. It’s important to choose a size that fits your specific needs. Window sizes that you’ll commonly see in homes include:
- 24 x 36 in.
- 30 x 40 in.
- 32 x 52 in.
- 36 x 60 in.
How do I know what window size I need?
To figure out what window size you need, you must measure at least the height and width of the window. You may also need to measure the depth and the opening clearance of the window. It’s always a good idea to have these measurements professionally made to ensure you pinpoint the size as accurately as possible.
What’s the difference between a window’s nominal size and its actual size?
A nominal window size is the size stated on most window sizing charts, usually as a four-digit number. The actual window size is usually about ½ in. smaller. The difference allows enough space for things like shims, caulking and flashing needed to install the window.
Can I get a window in a custom size instead of a standard one?
Yes, custom windows can easily be made for spaces where standard windows might not fit. They may be necessary in older homes or homes with alterations. Professional measurements can help you decide whether a custom or standard window is the best fit.