Confused about window sizes and standard window dimensions? Read on and we’ll explain everything you need to know about sizes when shopping for windows.

Do Standard Window Sizes Exist?

First of all, let’s address the fact that ‘standard window sizes’ are actually a myth. There is no industry-wide standard sizing, especially when so many windows are custom-made for houses. Standardisation of window sizes differ between manufacturers, who will make windows in sizes that they deem to be standard. 

As windows and houses are now mass-produced, this has led to an industry-wide standard of sorts, but again, it’s at the discretion of the manufacturers to decide what they think is standard. Those “standards” will also change over time.

Standard House Window Sizes

Before we get into the broad-stroke standard dimensions for house windows, let’s explain how these sizes are specified. There’s a really straightforward system for identifying window sizes. 

Window size is noted in a 4-digit figure. The first two digits refer to width and the other two are for height. For example:

4030 = 4 feet wide and 3 feet high

So, if you want a window that’s 38 inches wide and 68 inches high, its size would be noted as 3258. You may need a inches to feet converter (and vice versa)!

This is a handy way of immediately identifying and noting sizes, making it easier for you to shop. 

If you are currently undertaking a project, or want to know the ballpark ranges of common window sizes, then here are some new construction window sizes and average window dimensions:

Standard Bathroom Window Size

For this one, we’re going to look at two different standard window sizes. First, standard sliding window size:

Width: 36 to 84 inches

Height: 24 to 60 inches

Standard picture window size:

Width: 24 to 96 inches

Height: 12 to 96 inches

Standard Kitchen Window Size

You’re also likely to find picture windows in kitchens – the standard sizes for that is above. Another type of window commonly found in kitchens are double-hung windows:

Width: 24 to 48 inches

Height: 36 to 72 inches

For kitchens, it’s also handy to note standard casement window sizes:

Width: 14 to 35.5 inches

Height: 17 to 73 inches

Standard Bay Window Size

Width: 42 to 126 inches

Height: 36 to 78 inches

Standard Awning Window Size

Width: 24 to 68 inches

Height: 20 to 42 inches

Standard Sash Window Size

Width: 14 to 68 inches

Height: 24 to 128 inches

Things to Consider 

Window sizes are often in whole figures, but generally speaking they’ll be half an inch shorter than the specified number, as this makes installation easier. So don’t worry if your aperture is 37.8 inches high and the replacement window you want is 38 inches high. Double check with the vendor, but it should be still be fine for installation.

If your aperture will not fit a standard sized window, all is not lost. One option is to spend money on custom windows, but if you’re on a budget, this may not be viable. 

The most cost-effective thing to do is adjust the aperture so it will meet standard window sizes. This can’t always be done but if it can, it will certainly be less harsh on your pockets. Custom windows may be necessary in older homes, as they were built before windows were being mass-produced. 

For an outstanding range of Jeld Wen windows for your home, buy online today at Windows & More. We have selections of casement windows and sash windows as well as hand made bespoke windows that can cater to all of your needs. We also offer free shipping available to anywhere in mainland UK.