Firstly, you should note that roller blinds are generally not recommend for square bay windows, unless you have particularly wide corner mullions. This is because the width of the fabric is narrower than the overall width of the blind which means there will be areas of glass that are not fully covered by the fabric.
This is particularly noticeable with blackout roller blinds.
What you will need: A metal tape measure, a pencil & a piece or paper
Using a metal tape measure, measure the width of all three windows directly into the corners. Make sure to check the width at the top, middle and bottom of each window and record the smallest measurement.
Calculating the Width to Order Your Blinds
If you have any handles or vents on the windows, measure in millimetres how far out from the window frame they protrude. You’ll need to add this measurement to the ‘depth’ of your blind in the next step.
The ‘depth’ of your chosen blind type is shown in the table below. This depth is simply the distance your blind will protrude from where it is fitted. You’ll need to know this depth to make the correct allowance when measuring.
|Roller Blinds (Face-Fix)||70mm|
|Roller Blinds (Top-Fix)||50mm|
|25mm Real & Faux Wood Blinds||55mm|
|35mm Real & Faux Wood Blinds||55mm|
|50mm Real & Faux Wood Blinds||65mm|
|25mm Aluminium Venetian Blinds||30mm|
|Day & Night Blinds (Face-Fix)||75mm|
|Day & Night Blinds (Top-Fix)||55mm|
Add these two measurements together and note down the result as Dimension ‘A’. If there are no handles or any other obstructions on the windows, just use the blind ‘depth’ as Dimension ‘A’.
For the drop of your blinds, simply measure from the top of where you want the blinds to fit, down to where you would like the bottom of the blinds to rest (this is usually the window-sill, if you have one). Take this measurement in at least three places across the bay window and use the smallest measurement.
For Vertical Blinds only, reduce this measurement by 12mm to ensure the fabric louvres don’t drag or sit on the window-sill.
Note, all of the blinds for your bay window should be ordered as ‘Exact Size’.