How to Measure for Bay Window Blinds

Whether you've got a square 'box' style or angled bay window, we're here to help you get the right measurements to ensure your new blinds fit perfectly. 

With bay window blinds, the measurements you need to take differ for the type of blind you're looking to hang, we list the different rail width measurement allowances by blind type below.

Our handy guide makes measuring for your square, box or angled  bay window blinds simple, but as always, get in touch should you have any queries. 

What you'll need

•    A pencil
•    A metal tape measure
•    X2 pieces of A4 or A5 paper or card - for your template
•    A ruler


Step 1. Choose your Blind Type

First you will need to decide which type of blind you will be measuring for in your bay.

Roller binds

Please note: due to the cloth cover always being narrower then the bracket to bracket exact size,  unless you have large corner window frame work, there will always be areas of glass that aren't covered fully by the blinds, this is especially noticeable if you're looking to install blackout blinds. This applies to ALL roller blinds.
You also need to decide whether you will be  top or a face fixing as this will affect your allowances when measuring. Top-fix bracket allowance is 50mm(for blinds up to 2000mm wide), and 70mm(for blinds over 2000mm).


Wooden blinds

Firstly, you need to establish the rail depth for the slat size of wooden blind that you're measuring for using  the chart below.
Slat Size Rail depth
50mm slat wooden blind 70mm
35mm slat wooden blind 42mm

Vertical blinds

With vertical blinds, be careful when adjusting your measurements - you need to be aware of your bracket sizes when ordering this kind of blind for a box or square bay window.

Metal Venetian blinds 

 Option one is most commonly used for installing metal blinds onto square or box bay windows. Decide upon the slat width you require and then consult the table below.


Roman blinds

The rail depth  for our Roman blinds is 45mm.

Pleated blinds

The rail depth for our pleated blinds is 35mm.

If you need any further help with other blind types give us a call or send an email. contact us

Step 2. Measuring

Measuring for Square bay windows

There are two options for measuring and installing the blinds. Option one gives greater coverage across the front of the window whilst option two is best to give greater coverage to the sides.

Option one: Simply measure the full width of the bay, from one side to the other, and order this blind as a recess fitting. Do the same thing with the side windows (though be sure to measure both of them separately, as they may not be the same size), but this time deduct the rail depth from your measurements. These should also be ordered as a recess fitting, as you've accounted for the  blind's head rail but not allowed for any clearance between the blinds. 

Option two: Simply measure the side windows right up into the corner, and place the order as  recess fitting. Be sure to measure each side separately as they may differ. Next, measure the main front window section from corner to corner, and take away double the head rail depth, to allow for the side blinds projecting out. This means that the front blind will sit comfortably between the side blinds. Order the  blind as recess size.

NB: For all products and in both options above you will need to make further allowances for any protruding handles or other obstructions, that will interfere with the use of the blind. Add the measurement of the protrusion  onto the rail depth size given above. For Example: A handle protrudes 20mm plus 70mm for a 50mm  wooden slat option, requires a total deduction of 90mm to be made.

Measuring the drop: For both options, you simply measure from the top of where the blind will be fitted normally the underside of the ceiling, to the window sill or wherever you wish the blinds to hang to. The drop will be recess size and we will deduct our standard clearance allowance from your given size.

Measuring for angled bay blinds

The different blind type rail depths given above are referred to as  'Measurement A'  below.

What to do

Once you've got your measurement 'A', you can correctly measure the width of blinds needed for your angled bay window, as well as the drop length that's required. Be sure to always check every measurement twice!

Step one: Marking the angles
Using A5 card or A5 paper for example, you need to create two templates to represent the bracket projection of your blinds.  Align them so that their shortest edges are parallel to each other, and mark both of them with measurement A .Place these two pieces of paper on the window sill  up against your frame, one on the left side and one on the right of the angle and slide them towards each other until the marks you made on the papers meet (there will be a little overlap with the paper). 


Step two: Marking the window sill 
Using the pencil, clearly but lightly mark the window sill or frame where each short edge ends nearest to where the windows panel meet. This will  leave you with two marks on your frame or window sill, one either side of the 'corner' in the bay window. Now do this for the other angle of the window, too.( You may have more than the normal two angles/three panels, if so simply repeat the process for each).

Step three: Measuring the width
Using the edge of the window and the marks you've just made as your guide, measure the distance between the three separate sections (typically one larger, two smaller). This will be the width of the blinds that you need to order. Make a note of these measurements, and be sure to double check them. These will be your recess measurements. 

Step four: Measuring the drop
Measuring the drop: For both options, you simply measure from the top of where the blind will be fitted normally the underside of the ceiling, to the window sill or wherever you wish the blinds to hang to. The drop will be recess size and we will deduct our standard clearance allowance from your given size.

By now, you'll have all the measurements you need to order blinds for your angle bay window - just remember to order blinds as recess sizes. 


Get in Touch

0370 218 7042

0370 218 7042
Our standard office opening times:
9.00am - 5.00pm Monday to Friday
9.00am - 2.00pm - Saturday
Closed - Sunday
Our phone lines will be closed on Saturday 25/06/22. 
Please use our web contact form and we will respond to all enquiries when the office is back open on Monday.

Swift Direct Blinds Ltd. 177, Lockwood Rd, Huddersfield, West Yorkshire, HD1 3TG | Company No. 1190828 | VAT No. 184549920

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