Bay windows are the most beautiful architectural features that a house can possess. They drown in your rooms with sunlight, provide comfortable corners, and bring solemn curb appeal to any home. However, when it comes to covering them with blinds? Majority of home owners bumped into a wall.
The angles. The varying depths. The corner gaps. All of this is intimidating – more so when a miscalculation will result in the loss of money spent on tailor-made blinds that will not fit.
And here is the best news: it is quite possible to measure bay windows to install blinds on your own, provided that you take the right measures in the right sequence.
This tutorial takes you step by step on how to do it – not only do you get familiar with the structure of your window but you also get to write down your final measurements with a lot of confidence.
What Makes Bay Windows Different to Measure
You can learn the reason why bay windows are a special concern before you pick up your tape measure.
A typical flat window is a single-opening window. It has three windows, a big center panel with two angled side panels on either side. Such side panels are generally at an angle of 30, 45 or 90 degrees to the wall.
This creates two main challenges:
Corner gaps: Two panels always meet at an angle and as a result, there will always be a small gap between the blinds. The thinner your blinds headrail, the narrower that gap, hence the frequent use of 1-inch faux wood blinds and cellular shades in bay windows instead of more substantial ones.
Varying depths: Center panel and side panel may have different depths of sill. Do not ever think they are alike. Always weigh each part separatāely.
Get these two things and the rest is easy.
What You Need Before You Start
Gather these before taking a single measurement:
- Steel tape measure (not fabric — fabric stretches and throws off your numbers)
- Pencil and paper or your phone notes
- A step stool if your windows are tall
- A wide center panel helper (not mandatory but handy)
At this point also determine whether you would like an inside mount or an outside mount. This alters what you gauge and how.
Inside mount is used where the blinds are placed within the window frame. This provides a cleaner built-in appearance and it is most popular with bay windows.
Outside mount is when the blinds are attached to the wall or frame above the window. It is employed when the depth of your sill is too shallow to mount inside, or when you wish to give the impression of a bigger window.
Step 1 — Identify Each Panel of Your Bay Window
Label your three panels before measuring anything. Use a simple system:
- Left panel (angled, left side)
- Center panel (facing straight out)
- Right panel (angled, right facing)
You will take each one of these separately and have each one blinded. Do not attempt to wrap up all three panels in a single large blind, it will not fit the angles.
Step 2 — Test Your Sill Depth for Inside Mount
It is the most overlooked step in the guides and leads to the greatest problems.
An inside mount will only be effective when your window sill is deep enough to accommodate the headrail of the blind without sticking out of the frame. As a general rule:
- Minimum depth of most blinds: 1.5 inches
- Optimal depth to a flush, clean installation: 2.5 inches or more
- In the case of cellular shades and 1″ blinds in particular: 1.5 to 2 inches is generally enough
How to test it: Measure from the front of the window frame straight back to where the glass begins. Do this for all three panels — they may not be the same.
When any panel is less than 1.5 inches, you can either take an outside mount on that panel or select a narrower product such as a 1-inch blind or a cordless roller shade.
Step 3 — Measure the Width of Each Panel
To mount on the inside, take a width measurement of the window opening in three points; top, middle, and bottom. Bay windows may also be a bit lopsided as they settle with age, particularly in older Maryland and Virginia houses.
Write down all the three readings and apply the least measurement. This makes sure that the blind slides without jamming. Do not round up.
Write it down to the nearest 1/8 inch.
In the case of outside mount, gauge the extent by which you wish the blind to protrude on either side of the window frame – normally 1.5 to 3 inches. This, plus the opening width, makes the total. This additional coverage prevents light holes and enhances privacy.
Pro Tip: Take extra care with the two angled side panels. A quarter-inch wider than a side panel blind will bump against the center blind when both are up.
Step 4 — Measure the Height of Each Panel
In the case of the inside mount, the height of each panel is measured between the top of the inside frame and the sill of the window. Once again, measure in three points, left side, center, right side, and take the tallest measure as the height (not as the width, on which you would take the shortest measure).
In case of an outside mount, where you intend to place the bracket above the window, measure all the way to where you wish the blind to end, usually, sill or slightly below it to provide a clean line.
Record height measurements in 1/8 inch.
Step 5 — Account for Corner Gaps
Here is where bay window installs differ from a standard window. When you have three blinds in a bay window you will not have them meet at the corners, the angles physically will not allow it.
To minimize these gaps:
- Choose blinds with slim headrails. Cellular shades and 1-inch wood/faux wood blinds have the smallest headrail in the market. This makes the panels as close to each other as possible.
- Avoid products with wide valances or bulky cassettes. Roman shades are equipped with decorative hardware and roller shades have large cassettes.
- For outside mount only: When on a continuous exterior wall with no frame breakup one large blind can be ordered to fit all three panels. But that necessitates a specialty curved or angled headrail – see a professional before taking this direction.
Step 6 — Write Down Your Final Measurements
Having all these six numbers (width and height of each of three panels), arrange them as follows before you order them:
| Panel | Width | Height | Mount Type |
|---|---|---|---|
| Left | e.g. 24 3/8″ | e.g. 42 1/2″ | Inside |
| Center | e.g. 36 1/4″ | e.g. 42 1/2″ | Inside |
| Right | e.g. 24 3/8″ | e.g. 42 1/2″ | Inside |
Inside mounts will be deducted by most blind manufacturers, including the brands we have at BuyHomeBlinds, to make sure the blind slides in easily. You supply the precise aperture size – they do the calculations. Always make sure that this is checked with your retailer before ordering.
Step 7 — Choose the Right Blind for Your Bay Window
Now that you have your measurements, a little guide on what works best:
Ideal in limited spaces and shallow sills: 1-inch cellular shade or faux wood blinds. They both have slim profiles reducing corner gaps and can be easily fitted into shallow frames.
Best when a soft, fabric appearance is desired: Cordless Roman shades or roller shades. The panels are independent and therefore there is no chance of tangling or collision of adjacent panels.
Best for energy efficiency: Cellular (honeycomb) shades. Their air-trapping design suits large bay window opening which lose heat in Maryland winters and gain it in DC summers.
Best for a classic, timeless look: 1-inch or 2-inch wood blinds in a stain finish that complements your trim color.
Should not fit most bay windows: Plantation shutters (need excessive depth and clearance on the swing in tight alcoves) and curtains on curved rods (so hard to measure, hardware often does not allow full travel around the rod).
When to Call a Professional
Most of the typical bay windows work well with DIY measuring. Contact professional when:
- You have an odd angle in your bay window (not 30, 45 or 90 degrees)
- One or more panels are curved rather than angled (this is more common in bow windows)
- Your depths in sill differ radically between panels
- You have in mind motorized blinds on all three panels and would like them to operate together
BuyHomeBlinds provides a free in-home measuring consultation service to homeowners in Maryland, Virginia, and Washington DC. We do the measurements, suggest the appropriate product to fit your particular window set-up and also install everything on your behalf.
Final Thoughts
Measuring bay windows to make blinds is one such task that seems daunting but becomes easy the moment you divide it into steps. The secrets are easy: measure them individually, experiment with your sill depth before you invest in an inside mount, use a thin product profile to keep the corners to a minimum, and test and record your measurements within one-eighth of an inch.
We are BuyHomeBlinds, and we are always happy to assist you in case you are in doubt. Our products are offered to homeowners in Silver Spring, Bethesda, Northern Virginia, and Washington DC, in the form of a free in-home consultation, custom-fit blinds and professional installation.
Ready to get started? Contact us today for your free in-home measuring consultation.
Frequently Asked Questions Bay Windows for Blinds
Q: Do I need to measure each panel of a bay window separately?
Yes, always. Although the panels may appear the same, they are not often exactly the same size. The only measure that can be taken to make sure that every blind fits is to measure each one separately.
Q: What is the minimum sill depth needed for inside mount blinds on a bay window?
A depth of 1.5 inches is the lowest sill depth needed with most blinds to install inside. Cellular shades and 1-inch shades may frequently be used with a little shallower depth. When your sill is less than 1.5 inches, an outside mount is a safer option.
Q: How do I stop gaps at the corners of my bay window blinds?
Select blinds that have the thinnest headrail – the best ones are faux wood blinds and cellular shades that come in 1-inch. The wider the headrails, the larger the gap at each corner angle. Roller shades also have bulky cassette housings which add to the gaps that are seen.
Q: Can I use one large blind to cover all three panels of a bay window?
In most cases, no. The physical impossibility of the single flat blind covering all three parts without bunching or binding is realized by the angles between the panels. There should be a blind of the panels separately measured and ordered.
Q: Should I measure inside mount or outside mount for a bay window?
Almost all bay windows will be better constructed with an inside mount as it holds the blinds inside the frame and provides a smaller gap at the corners. Outside mount is only applied when the depth of the sill is too small to include an inside mount.
Q: What type of blind is best for a bay window?
The three most recommended would be 1-inch faux wood blinds, cellular shades, and cordless Roman shades. They are all thin-profiled, they can easily be mounted in angled bays, and they have a small corner gap problem that the more substantial window treatment suffers.
Q: How do I measure a bow window differently from a bay window?
Bow windows consist of four or more panels, which are positioned in a soft curve, and not sharp angles. The same method of measurement is used, measuring each part separately, width and height, but the angles between the panels are more gradual. This implies that corner gaps tend to be less, and you can be more flexible with the product.
Q: Can BuyHomeBlinds measure my bay windows for me?
Absolutely. We provide a free in-home measuring service to Maryland, Virginia and Washington DC homeowners. Our consultants will do all measurements and even installation to make sure that your blinds are fitted the first time.