What are standard window sizes?

In the Chicago area, most homes are over 30 years old—some even 50 years old. These older homes were typically built with standard window sizes, but over time, shifting structures and outdated designs can make finding the right fit a challenge.

According to Energy.gov, “Heat gain and heat loss through windows are responsible for 25%–30% of residential heating and cooling energy use.” That’s why choosing the right new or replacement windows—and making sure they’re properly sized—is essential for improving energy efficiency.

Each manufacturer has its own definition of a specific window size, and with so many different types of windows on the market today, it’s important to know what works best for your home.

The average homeowner may not realize how much variation exists between brands and styles, so take a moment to research your options before cutting a rough opening in your wall.

Following this guide will save you time and money.

Common window sizes and window types

Whether you’re looking for new windows or replacement windows, knowing a thing or two about the most common window types will help you make an informed decision. A common window is usually available in standard sizes.

Single-hung and double-hung windows are among the most popular choices for both new houses and replacement windows.

While single-hung windows have a fixed upper sash and a mobile lower sash that moves up and down, double-hung windows have both sashes mobile.

Bay windows delight with plenty of natural light and are more appealing due to their design while picture windows allow the beauty of your view to invade your home. However, picture windows have the disadvantage of being fixed windows that can’t be opened.

Sliding windows are often preferred for newer houses and are ideal for small spaces that require plenty of ventilation, such as the kitchen or bathroom. In fact, windows are the most common features upgraded during renovations due to their impact on comfort and energy efficiency.

Ideal for a rainy climate, an awning window is hinged at the top and opens outward, protecting the interior from rain. Standard awning window sizes are available to fit most spaces, though custom options also exist. A casement window is another popular option, especially since it offers unobstructed views and excellent airflow. These windows open by swinging to the side or up.

Each of these window styles is available in standard sizes and is a perfect match for a variety of homes. However, to choose the right fit for your home’s rough opening—whether for new or replacement windows—it’s important to understand window dimensions and how they relate to your space.

Window Height

When measuring window heights, you need to measure from the high point of the sill to the top of the window opening. Be sure to write down three measurements: one at the left side, one at the center, and one at the right side of the window. When you order the window, you will need to use the smallest measurement of the three to ensure a proper fit.

For sliding window sizes, which are typically wider than they are tall, getting the correct height is just as important as the width. Always compare your measurements to the standard heights available from manufacturers, but keep in mind that the actual size of your window may vary slightly based on your home’s construction or age.

Window Width

To determine your home window width, measure between the jambs at the top, middle, and bottom of the opening. Just like with height, use the smallest measurement when placing your order for windows for your home.

Keep in mind that the correct width measurement will vary depending on the part of the window you’re assessing, and the final size of the window depends on both the rough opening and the specific window style you choose. Whether you’re ordering a common window type or a custom design, accurate measurements are key to a perfect fit.

Window Depth

Window depth measurement doesn’t include pulleys and parting strips and needs to be made at least 3 ¼ inches of opening depth between the inside window trim and the outside blind stop strip.

Rough Opening

An important part of the measurement process, the size of the rough opening is established by measuring from the inside of one side of the window frame to the other.

Manufacturers decided to simplify the window sizing process by delivering standard window sizes and using a simple window size notation.

The notation is the combined width and height, and is always a whole number for the rough opening, even though the actual measurements are usually ½ inch less.

A 2426 window measures 2 feet, 4 inches by 2 feet, 6 inches. The first two numbers are for the window’s width, while the second two define the window’s height.

Window measurement notation examples:

2020 windows – designed to fit a 2-by-2-foot rough opening and measures 23 ½ by 23 ½ inches.

3838 windows – designed to fit a 44 by 44 inch-rough opening and measures 3 feet, 8 inches wide by 3 feet, 8 inches long

Standard window sizes

Standard window sizes vary depending on the type and size of the window you’re planning to use for your home.

Manufacturers take into consideration the rough opening sizes when establishing their standard window sizes, but knowing standard dimensions ahead of time can help avoid delays when you’re ready to install new windows.

However, keep in mind that they always take off a ½ inch on both the window width and height ranges to ensure proper installation and function. The ½ inch allows the installer to easily fit the window and secure it afterward with shims.

Here are the most common sizes for standard windows. These sizes include options for both new construction and replacement projects:

Double hung windows:

• Width: between 24 and 48 inches
• Height: between 36 and 72 inches

Picture windows:

• Width: between 2 feet and 8 feet (standard dimensions: 2 ft, 3 ft, 4 ft, 6 ft, 8 ft)
• Height: between 1 foot and 8 feet (standard dimensions: 2 ft, 3 ft, 4 ft, 5 ft, 6 ft, 8 ft)

Sliding windows:

• Width: between 36 and 84 inches (standard dimensions: 36 in, 48 in, 60 in, 72 in, 84 in)
• Height: between 24 and 60 inches (standard dimensions: 24 in, 36 in, 48 in, 60 in)

Bay windows:

• Width: between 3 feet, 6 inches and 10 feet, 6 inches
• Height: between 3 feet and 6 feet, 6 inches

Casement windows:

• Width: between 1 foot, 2 inches and 2 feet, 11.5 inches
• Height: between 2 feet, 5.5 inches and 6 feet, 5.5 inches

Awning windows:

• Width: between 2 inches and 3 feet, 10 inches
• Height: between 1 foot, 8 inches and 7 feet, 8 inches

Custom window size

And there are always the custom size windows that need to be manufactured based on the exact measurements of your home’s rough openings, especially if you’re looking for a specific size and shape you want.

The type of window you choose also plays a big role in determining sizing. A window’s dimensions usually depend on several factors: the year your house was built—the older the house, the less likely it is to match today’s popular sizes; the age of your home—time and weather may affect the rough opening; and the architectural style—classic homes often require different windows than modern designs.

Whether you’re buying windows for new construction or replacement, here’s what you need to know about window sizing before you make your decision.

Conclusion

Now that you’re familiar with the measurement process and know a few things about standard window sizes, you’re ready to proceed with your order for new windows or a window replacement.

However, you should remember that even though measuring and finding the right window sizes for your home seems simple and straightforward, once you’re face to face with the actual rough opening or window, there may be some hesitation. Different window manufacturers may offer standard sizes, but slight variations can still impact the fit and performance.

Choosing the right window styles and getting an accurate measurement is key to finding a perfect match for your house—and avoiding costly setbacks in your home improvement project.

Call the Chicago Window Guy to take care of both the measurement and installation of your windows. Save precious time and money!

Post Update: The article was updated on April 07th, 2025, and originally published on February 20th, 2020. It has been completely revamped and updated for accuracy and comprehensiveness.