How to Choose Bay Window Sizes

No matter if you plan to install a sliding or double-hung window in your home, you need to think about the size and the price. This is especially true if you have plans involving bay windows because they can help you add dimension and a touch of class or elegance to your outdoor areas. Along with this, they allow more light to filter in compared to other styles of windows. So, this is why it’s important that you learn about the various bay window sizes and their prices.

Generally speaking, bay windows are angled on two sides and will protrude out from your home at a 30° or 45° angle. They come in many sizes, so any size you may need for your home will be available, and this size ranges from the smallest option up to oversized ones. We’ll outline how to choose bay window sizes below.

1 Kitchen Bay Window
Bay windows are very elegant and functional additions to homes that can boost the home’s value.

Defining a Bay Window

A bay window is actually three windows with one big fixed window in the middle and a smaller window situated on each side. The two smaller windows that flank the big one can be casement, fixed, double-hung, or single-hung windows. Due to their extension past your home’s wall, bay windows give you a much broader view of your yard or surroundings. These windows are very popular with homeowners because they have the ability to capture larger amounts of natural light from different directions.

If you take a look at specialty windows in general, bay windows are one of the most functional you can get. They add dimension and space to the inside of your home. Because the design has it jutting out from the wall, it has a deep sill area that allows you to create a cozy reading nook or shelf that you can decorate or use to display plants. Generally, your bay window size is meant to accommodate spaces with a minimum of 42-inches of room or more.

Popular Bay Window Types

In the medieval era, bay windows were completely ornamental. But, over the centuries, architects performed many experiments with this type of window. As a direct result, there are currently many types of bay windows on the market, and this is why bay window sizes and prices fluctuate so much. Some of them offer a huge amount of types and offer unique but rare designs, and other types are much more common and accessible. The following are some of the most common bay window types you can get:

Bow Bay Windows

First up is the bow bay window, and this type is very useful if you want to get a very scenic view outside. As the name suggests, this window comes with a curvature that sticks out of the home. You place three or more casement windows together in a line to get them the classic outward look. These types of bay windows won’t be low enough to touch the floor, so you can see them on the ground floor or on second or third storeys without a problem. This type of bay window is larger than Box or Oriel bay windows, and they have a different purpose. You can get a larger view of your space and more light in with gentle curves that match a huge range of design aesthetics.

Box Bay Windows

When you get a box bay window, you’ll get a window with a square shape to it that mimics the look of a box. Generally speaking, these windows will be more rectangular than square, and this bay window type usually comes with flat sides and a flat front and flat roof. You can find this type of window all over the UK, and it’s also very popular in western Europe.

The side on this bay window won’t have that gentle angle that other bay windows do. If the side is angled, then the name switches to a Canted bay window. The depth of your window will depend on the angle it forms with the wall of your home. So, a 30° box bay window will have a 12 to 14-inch depth. If your window has a 45°, the depth will range from 16 inches up to 22 inches, and most box bay windows are between 18 and 24 inches deep.

2 Box Bay Window
Box bay windows are very popular in the UK instead of in the United States, and they offer a very sturdy look and feel.

Canted Bay Windows

We touched on canted bay windows very briefly above, and they’re very similar to the box bay windows. It comes with the shape that is the ideal classic bay window, so it fits many decors. It usually comes with a flat front, just like you’ll see on a box bay window, but the sides will both be angled. You can find canted bay windows located on the ground or first floor of a building or home. Also, canted bay windows are extremely popular in Victorian home design. You can have three, four, or sometimes even more windows making up your complete canted bay window.

Circle Bay Windows

Circle bay windows are one of the most evolved bay window types you can get. Architects have done so many experiments on this window over the centuries, and you usually get a much rounder shape with them. To get this shape, you will combine several smaller windows into a single round one, and you typically put this window in the corner of your home. This is a slightly bigger bay window size, so the price will be higher. It’s also much more ornamental than most bay window designs. Generally speaking, you usually couple this window with circular window seats that make a very elegant and beautiful look. It can be up to six feet high and extend two or three feet past the wall of the house.

Oriel Bay Windows

Oriel bay windows are the oldest type on the market, and they first got very popular during the English Renaissance period. Usually, you’ll build this bay window at one side of your home, and it will never touch the ground. You can also find them on higher storeys in the home, and you’ll need to add a decorative wood or stone corbel or bracket under the window to provide more support for it to ensure it stays in place. The bay window size for this type usually stretches from 18 feet by 9 feet. However, you can find larger or smaller options too.

Do You Need a Bay or Bow Window?

If you’re getting to a place where you find yourself replacing your windows, there are many things to consider when you decide if you need a bay or bow window and the size you want. The nice thing about this is that many bow or bay window sizes can be customized to fit your design specifications as long as the window dimensions meet your local building codes.

Height could be one restriction that you have to consider, and you ideally don’t want your window more than 44 inches off the floor so that you can easily see outside when you’re sitting down. Other considerations include whether you want to pay for custom bay window sizes or if you’re willing to go with more standard options.

Where will you install your new bay window? Which room do you plan on putting it in? This will help you determine how much natural light you want your bay windows to allow to filter into the room. However, just as important is asking which direction the room is facing. Is it south, north, west, east, or a combination? Talking to a contractor will help you make the best choices when it comes to bay window sizes, design, and type to help ensure that it matches the room you want to put it in.

It may be more helpful in the long run to avoid talking about specific bay window widths and heights as you can usually customize them a bit. Instead, you want to talk about bay window proportions and consider bow windows. Consider any three-panel bay window as a whole, and it’s a good rule of thumb to make the outward-facing panel make up roughly half of your total window space. Round up the side panels at roughly a quarter of an inch, and the side windows can be double or single-hung or casements. Another option is to make each panel take up a third of the total.

For bow windows, the ratio will depend on how many panels you want to add. So, for example, if you have your heart set on a five-panel bow window, each panel will take of a fifth of the window space to get an even finished look.

Bay vs Bow Window

How do you tell the difference between a bay window and a bow window? Luckily, you can usually tell very easily which is which when you see them. Both types of windows will “bow” outwards and protrude from the side of the home, and this allows them to extend the size of the room by giving you a small interior bay. However, if you look at definitions, a bay window will only have three window panes in the design.

A bow window, on the other hand, will have four or more panes. A bay window will work to create a bigger interior space and can angle further outward from the wall. Bow windows, depending on how many panes you want to use, will create a more curved, shallower, and less angular profile that juts out from the side of the house. In turn, you get a smaller interior bay.

3 Box vs Bow Windows
Bow windows are usually more decorative than bay windows, but this can also make them much more expensive to buy and maintain.

Standard Bay Window Sizes

A bay window typically features three windows that you combine and get manufactured to make one big window unit. These three windows are usually connected using mullion posts, and the middle window is typically a casement window. One thing you have to note is that there are no fixed standard bay window sizes. However, the most common bay window sizes that most people choose to use range from three feet and six inches to ten feet and six inches wide. In contrast, the height of your bay windows will vary from the standard three feet up to six feet, six inches. This is one of the most cost-effective options you can get for bay window sizes since it can easily fit into a standard-sized window if you’re doing renovations on your home.

45° Bay Window Dimensions

The bay window size that protrudes at a 45° angle will have several widths and heights to choose from, depending on which window configuration you want to get an install. Typically, only the center window will offer a variety of venting configurations that you can get that ranges from a popular stationary center window to picture windows or more oversized options.

A traditional 45° bay window that has a stationary or venting center will have a width that ranges from 45 ¾-inches to 91 ¼-inches. In contrast, the heights for your bay window sizes will start around 26 ⅛-inches and go to 73 ⅞-inches. The projection of this bay window size will start at 14 3/16-inches and go to 27 ½–inches for the typical measurements.

At the same time, your 45° bay window with a fixed picture window in the center will have a width that ranges from 66-inches to 127 ¼-inches, and the height will range from 38-inches up to 61 ⅞-inches. Most standard bay window designs will feature a 45° outside angle compared to a traditional garden window that has a 90° outside angle.

Traditional Bay Window Angle

The term “bay window” is an umbrella term that encompasses all window constructions that protrude out from the side of the house, no matter the height. Since your bay window will protrude out at an angle on the outside of your home, it’s essential that you know what the traditional bay window sizes and angles are. The most common traditional bay window will have a normal inside angle of 90° to 135°. Once the degree hits 120°, you will classify it as an Oriel Bay Window, and this type curves much less than it angles.

Bay Window Depth

The depth of your bay window will depend on which angle you want it to protrude. There are generally two window angles available for your bay window, and these are window setups that will protrude at 30° and 45°. A 30° bay window size will usually have a depth that ranges from 12 to 14 inches. In contrast, a bay window with a 45° angle will have a depth between 16 and 22 inches to ensure that it’s a sturdy option.


Knowing how far your bay window will stick out or protrude from the side of the house is vital, especially if you want to do something right outside of the window, like tend your foundation plants. How far your bay window sticks out will depend on the window’s depth. However, most outward projects can be as short as 12 inches, and this can easily expand out several feet. If you plan to have a design that is deep enough to hold shelving units and decor items like a kitchen bay window, or a custom window seat, you need to consider structural integrity and spacing very carefully.

4 Bay Window Depth
How deep your bay window is depends on how far you want it to protrude from the wall of your home.  

Bay Window Benefits and Drawbacks

Every type of window in your home comes with benefits and drawbacks, including bay windows. No matter what your bay window sizes are, you want to know the benefits and drawbacks associated with them to see if they’re right for you.

Advantages of Bay Window

Below, you’ll be able to take a look and see the biggest benefits of this style of window and to choose the correct bay window sizes to match your needs and wants. The biggest benefits include:

  • Bay windows can work to create more area inside of your room, and this makes smaller rooms look bigger. They also create more space where sitting couches, decorative elements, flower vases, or air plants can go.
  • Bay windows make very elegant and beautiful outward appearances on your home, and they represent elegance and class. They introduce a one-of-a-kind look to the house, and they are very functional.
  • Looking out bay windows, you can get a larger view of your yard or garden. As most bay window sizes tend to run larger overall, you get a viewing angle that is much bigger than traditional windows. So, this allows you to look over your whole yard without a problem.
  • The larger bay window sizes that are available will automatically improve the lighting conditions in the room you choose to install them in. Large windows allow more natural light in, and if you choose to have colored glass put in, they create a stunning look.
  • These windows can boost your property value and curb appeal at the same time. Beautiful windows that form a straight line on the outside of your home with a traditional design and small ornamental touches increase your home’s value.
  • The two sides of your bay window usually aren’t fixed, but the middle pane is. So, you can open and close the two sides to bring in much more ventilation to the room on warm days.

Disadvantages of Bay Window

Along with all of the advantages these windows bring you, they also have some disadvantages that you want to consider. We’ve picked the three biggest ones and outlined them for you below:

  • Bigger space may be good, but you may not want more light in the room. Not only can this heat up the room, but it can make it too bright during those long summer afternoons.
  • No matter your bay window size, they’re more expensive than traditional windows. The maintenance will also be more expensive, so they’re not great for people who have a more limited budget. Also, it may not be possible to replace a broken bay window, so you have to add them when you build the house itself instead of going in later and adding it to an existing room.
  • The maintenance needed for bay windows in general, but especially for Circle and Oriel bay windows isn’t cheap or easy. It’s also not something you can DIY. You’ll need to bring in a professional to take on this task, and it’s usually very involved and expensive.

Bay Window Sizes – FAQs

5 Bay Window Size FAQs
Even though bay windows are very popular, it’s common for people to have questions surrounding them if they’ve never dealt with them before. A few of the most commonly asked questions about bay window sizes are below.

1. How much will it cost to install a bay window?

The average cost to install a bay window, regardless of the size, is between $1,150 and $3,550 per window. You will still need to factor in local labor costs, and this could easily top $40.00 an hour. However, this can vary from $300 to $500 for the project.

2. How much does it cost to replace a bay window?

To replace your bay window, you’ll typically pay around $1,800 per window. The labor aspect is between $100 and $300 for the project. Other factors that can impact the final cost of the installation is the type of window, where you want it, and the bay window size.

3. What are the most popular materials for bay windows?

Vinyl, wood, and clad are the three most common materials people use to create bay windows. Vinyl offers the advantage of no maintenance while being affordable, but not everyone likes how it looks. Wood frames need painting or staining periodically to prevent rot, and clad windows are the most expensive but have the lowest maintenance needs.

4. How do you correctly calculate your bay window’s area?

Some people talk about calculating the area of your bay window and think that this is an extremely complicated process. However, it’s actually much easier than it sounds, and it only requires basic math with precision measuring. The first thing you need to do is add up the individual areas of the floor areas of your bay window. A window bay usually has a square and a triangle, so assuming that the square is 12 feet while the triangle is 6 feet, you’ll get the square footage of 18 feet.

5. What is the smallest bay window?

The smallest bay window sizes are the standard ones with a width of three feet, six inches and a height of three feet. This is the size that will fit the most common window spacing measurements while offering a 180° view that more oversized bay windows have.

6. How deep should you make your bay window?

Your bay window’s depth will depend on what angle you want it to protrude out of. There are usually two angles you can choose from for this window style, and those are bay windows that protrude at a 45° tilt or at a 30° angle. A 30° bay window size will usually offer a 12 to 14-inch depth. In contrast, a bay window with a 45° tilt will offer a depth of 16 to 22-inches.

7. How do you measure correctly for a bay window?

The first thing you want to measure is the size of each window panel. There are three measurements to every bay window, and it usually involves measuring the width and height of each of them separately. Next, you want to measure the depth from the front of the second window pane down to the middle of the central pane. Last, you’ll measure the total width by finding out the distance from left to right.

Bottom Line

Now you know the common bay window sizes and styles, and you can use this guide to decide which one is going to work best for your needs, wants, and space. If you get it right, you’ll get a gorgeous addition to your home that raises your property value and boosts the curb appeal at the same time.

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