We’re all familiar with standard clothing sizes: S, M, L, and XL. But did you know that windows come in standard sizes? Most homes conform to this standard sizing system, making construction and manufacturing easier.
The average cost to replace standard-sized windows ranges from $6,408 to $11,659, depending on the size, material, and number of windows. But if your existing windows are not standard, you'll need custom-made windows, and the cost to replace custom windows is considerably more. So, if you plan to install new windows in your home, knowing what types of windows you have and their standard sizes helps you compare options that fit the existing openings.
Continue reading to learn about different kinds of home windows, their standard sizes, and when you need custom-made windows.
Key takeaways
Window manufacturers assign codes to windows that indicate size. Know the code, and you're in the club.
Standard window sizes differ by type or style of window.
If your windows aren't standard sizes, you can order custom-made windows or change the size of the openings.
Window manufacturers assign four-digit codes to windows that indicate window dimensions. The first two digits indicate the feet and inches of the width, and the last two indicate the feet and inches of window height. For instance, window 2044 is 2 feet, 0 inches wide, and 4 feet, 4 inches tall. Understanding window size notation will help you shop and compare options.
Standard window sizes
Standard window sizes depend on the style of the window. Here is a breakdown of the most common window types and their standard sizes.
Standard sizes of double-hung or single-hung windows
Single-hung and double-hung windows are the most common windows in homes and are similar in appearance. The difference is that only the lower sash moves up and down in a single-hung window, while in a double-hung window, both sashes move. This style is preferred for two-story homes where you want to protect children from falling out of the opening. The following sizes are typical for these windows.
2 feet wide by 3 feet high (2030)
2 feet wide by 4 feet 4 inches high (2044)
2 feet 8 inches wide by 4 feet high (2840)
2 feet 8 inches wide by 5 feet 2 inches high (2852)
Standard sizes of sliding windows
A sliding window has sashes that move from side to side instead of up and down. It provides more airflow and natural light than single- and double-hung windows. And, without the horizontal rail in the middle of the window, the view from a sliding window is unobstructed. Here are the standard sizes of sliding windows.
3 feet wide by 2 feet high (3020)
3 feet wide by 3 feet high (3030)
5 feet wide by 3 feet high (5030)
6 feet wide by 4 feet high (6040)
Standard sizes of picture windows
For that picture-perfect view, homeowners prefer a picture window. Though they don’t open, the exchange for light and scenery is worth it. They’re often found in the living room or family room. Here are standard picture window sizes to consider.
3 feet wide by 2 feet high (3020)
5 feet wide by 3 feet high (5030)
6 feet wide by 4 feet high (6040)
4 feet wide by 5 feet high (4050)
Standard sizes of awning windows
An awning window is hinged at the top and cranked open. Typically wider than tall, awning windows are commonly used high up in the wall of a mid-century modern design or as a transom above a door. The standard sizes of awning windows include:
3 feet wide by 2 feet high (3020)
4 feet wide by 2 feet 4 inches high (4024)
5 feet wide by 3 feet high (5030)
Standard sizes of casement windows
Like a sliding window, casement windows lack the horizontal rail that blocks your view of the beautiful outdoors. Usually, they’re taller than they are wide and crank out from the side like a door. Here are the standards for casement window sizes.
2 feet 4 inches wide by 3 feet 6 inches high (2436)
2 feet 6 inches wide by 4 feet high (2640)
2 feet 8 inches wide by 5 feet high (2850)
3 feet wide by 6 feet high (3060)
Bow window and bay window sizes
Bay and bow windows are created by placing numerous windows side by side. For instance, a bay window generally includes a picture window in the center with a double-hung window on each side. The total size of the bay window depends on the double-hung window sizes and the picture window measurements. Due to these variables, we don’t include standard height or width ranges for these styles.
How do I measure my window?
To correctly measure your window before ordering a replacement, follow these steps:
Make sure your window frame is square by measuring diagonally from corner to corner in both directions. The measurements should be within 1/16- to ⅛- inch the same. If they’re not, you need to hire a professional window installer for this project.
Measure the window width between the jambs at the widest part three times–at the top, middle, and bottom. The smallest measurement is the width.
Measure the height inside the window from top to bottom in three locations–far left, middle, and far right. The smallest measurement is the height.
With the window open, measure the depth from the inside of the interior to the inside of the exterior trim. You’ll only need this measurement if you live in a mobile or modular home. Otherwise, all windows are the same depth.
Round all the measurements down to the nearest ⅛ -inch.
To ensure you get accurate measurements, check out our in-depth, step-by-step tutorial on how to measure your windows yourself.
A homeowner can get accurate enough measurements to get an estimate; however, we always have a certified measure tech who will do all final measurements to ensure proper fit, identify any issues that need addressing, or see if extra materials are needed.
What is a rough opening?
The rough opening (RO) size refers to the frame dimensions to which the window attaches. "It's the original stick framing of that house, the opening that the window is supposed to fit in," says Andrew Prchal, president and co-founder of Gunner. The frame includes a header at the top, a sill plate across the bottom, and a vertical trimmer on each side. This size is larger than the window size. Once installed, insulation fills the space between the rough opening and the window unit to improve energy efficiency. "And then trim is installed around it to create a beautiful aesthetic," Prchal adds.
What if my window isn’t a standard size?
Unlike new construction, older homes may not have common window sizes. If your window opening isn’t a typical size or odd shape, you’ll need to order a custom-made window. A custom window will add to the project’s time frame because the window will need to be designed and manufactured. This process includes cutting glass to the desired shape and dimensions and building a frame to match. A custom window is more expensive than purchasing a standard window off the shelf. However, custom-size windows are not limited to specific standards.
Can you change the size of a window opening?
The average rate for a carpenter to resize a window opening is $58 to $106 per hour, depending on your location.
Yes, you can change the size of a window opening. However, enlarging the size of the opening is more complex than making it smaller. "The header, which is the support beam above the window, would remain unchanged if you're making it smaller," says Prchal. "But if you're expanding the window size, you have to expand the size of the header to accommodate the new opening." So, unless you have construction framing experience, it’s best to hire a professional to expand the size of your window.
To shrink a window opening, you simply need to add wood framing to the existing rough opening. However, homeowners must remember that they have to cover the space on the exterior with new siding or brick; for that, they may need professional help.
That said, windows in bedrooms and basements must adhere to specific sizes to provide a way of escape in an emergency. While not a window style, these windows are referred to as egress windows. They must be openable and meet size requirements set by building codes. According to Jay Sander, licensed contractor and owner of Maryland Contractors, a good rule of thumb is to have a 5.7-square-foot opening for a bedroom egress and a 9-square-foot opening for a basement one. But always check with your local building department for the codes for your area.
Final thoughts on standard window sizes
Becoming familiar with different types of windows, common widths, and height ranges helps you make the right decisions for your home improvement projects. If you’re like most homeowners, you’re not ready to DIY a window replacement. So, let us help you find a local window installation specialist in your area. Most offer a free quote and can discuss the finer points of window brands, warranty specifics, and the best windows for your home.
FAQs
Egress window sizes vary by state. If you're replacing your windows yourself, always check with your local building department for code requirements.
That depends on the house and its age. However, window manufacturers standardized window sizes by the mid-1900s, so you have nothing to worry about unless your home is older than that.
No. The rough opening is slightly larger than the window to accommodate installation and insulation.
Standard sizes for a sliding window include 3020, 3030, 5030, and 6040.
Carol J Alexander is a home remodeling industry expert for Fixr.com. For more than 15 years as a journalist and content marketer, her in-depth research, interviewing skills, and technical insight have ensured she provides the most accurate and current information on a given topic. Before joining the Fixr team, her personal clients included leaders in the building materials market like Behr Paint Company, CertainTeed, and Chicago Faucet, and national publications like This Old House and Real Homes.