How to Measure for Blinds in a Bay Window

Bay windows require some special measurements to ensure you get that beautiful fit in your windows

How to Measure for Bay Windows

Whether you’ve got an multi-aspect 6-pane bay window, or an awkward box bay that needs some shading, we’ve got you covered. Below are instructions for measuring bay and bow bay windows, plus two options for box (or square) bay windows. Pick the instructions that best match your window. And don’t forget, if you need any more assistance when measuring we're always available via phone or live chat.

You will need:

Angled Bay Measuring Instruction Video

Step-by-Step Angled Bay Measuring Instructions

  • Step 1

    Before your begin, ensure you've ordered one of our free sample packs. Included in these are measuring templates that make measuring for bay windows as simple as possible. 

  • Step 2

    Check for any obstructions around your window, such as handles or air vents. If you do have any obstructions, you’ll need to take these into account. Measure the distance between the front of the window frame and the outer edge of the obstruction. This is shown as ‘A’ in the diagram below. Make a note of this measurement.

  • Step 3

    You will need to add this measurement to the depth of your desired blind. For example, if you are installing aluminium blinds, with a headrail depth of 3cm, and your measurement ‘A’ from the diagram above is 4cm, the effective depth of your headrail is now 7cm. So on our guide, you would use the 7cm mark on the bay window card.

  • Step 4

    Next, mark your measuring points on your window sill. Lay your measuring guides flat on the window sill, against the face of the window frame. Move the two guides towards each other until the arrows (your effective headrail depth) meet.

  • Step 5

    With the two measuring templates touching, you’ll need to make a small pencil mark on the window sill where the edge of the measuring template meets your window frame. You now have your first measuring point. Repeat this step for each angle in your bay. For the windows on the outer edge of the bay simply make a mark where you’d like your blinds to stop.

  • Step 6 

    Now you have your measuring points, it’s time to measure the distance between them. This will give you the width of the blind you need to order. Repeat this step for all windows.

  • Step 7

    Now, measure the length of your windows. We recommend taking three measurements to ensure accuracy. Make note of the smallest measurement. This measurement will be the ‘drop’ when ordering your blinds.

  • Blind Headrail Deductions and Step 8 - Let's order!

    Now you’ve got your measurements you’re ready to place your order. When ordering your blinds, we recommend selecting the ‘recess’ option. When this option is selected we will make a small deduction from the width to ensure a snug, yet easy fit.

    If you’d prefer to make a small deduction from the width yourself (we recommend 1.2cm) then do so and order your blinds as 'exact' size - depending on the product you’re ordering. 

  • This guide covers 3-pane bay windows, but you would just need to repeat this process for a 4, 5 or 6 pane window. 

  • Please Note: If you have any questions about bay windows, including where you will be installing the blind, we are always on hand to help. Each window is unique and can have additional obstructions that may not be covered above - including things like decorative plastic trim around the top, picture rails, windows without an obvious install point and windows that sit flush with the wall. 


Box Bay Measuring Instructions

Step-by-Step Square or Box Bay Window Measuring Instructions - Option 1

Use these instructions if you want the front of the bay window, usually the largest window in the bay, to span the entire width of the bay, and the two return blinds to overlap the large one. This is the most popular way to install in a square bay as it provides maximum coverage from front-on.

It’s important to note that some blinds have a minimum width they can be made to, so make sure the smaller return blinds on either side exceed the minimum width of your chosen blind style. The minimum width is listed on each product page.

  • Step 1

    Measure the total width of the front bay window. Usually this is the largest window in the bay, shown as ‘A’ in the diagram below. Measure to the nearest millimetre. This number will be your width measurement when ordering your blind.

  • Step 2

    If you have handles on your bay window you’ll need to account for how much they protrude. Measure out the distance of your handle, air vent or any other obstruction from the window frame. Make a note of this measurement, shown as ‘B’ below.

  • Step 3

    Now combine the depth of the blind and the handles you've just measured for. Measure this distance away from the main window and mark this point. This combined distance is shown as 'C' on the diagram. The headrail depth can be found on the next table. 

  • Blind Headrail Deductions

    When making the deductions for the headrail depth, please use the measurements below. 

    Blind TypeDeduction
    Aluminium 30mm
    Roman 50mm
    Top Fix Roller Blind 50mm
    35mm Wooden Blind 65mm
    50mm Wooden Blind 75mm
    Vertical Blind 75mm
  • Step 4

    Measure from the pencil mark you’ve just made to where you would like the blind to finish, shown as ‘D’ in the diagram below. This is the width of your ‘return’ blind. Make sure you measure both sides, as the sizes may be slightly different.

  • Step 5

    Now, measure the length of your windows. We recommend taking three measurements to ensure accuracy. Make note of the smallest measurement. This is the ‘drop’ measurement when ordering your blinds.

  • Step 6 - Let's order!

    Now you’ve got your measurements you’re ready to place your order. When ordering your blinds, we recommend selecting the ‘recess’ option. When this option is selected we will make a small deduction from the width to ensure a snug, yet easy fit.

    If you’d prefer to make a small deduction from the width yourself (we recommend 1.2cm) then do so and order your blinds as 'exact' size - depending on the product you’re ordering.

Step-by-Step Square or Box Bay Window Measuring Instructions - Option 2

Use these instructions if you want the two side windows in a square bay to span the full width of the side window returns and for the large, front bay window, to sit between them. This is usually used when the side windows are very narrow and we are otherwise unable to manufacture blinds small enough. The minimum width of each blind is listed on the product pages.

  • Step 1

    Measure the total width of the side bay windows into the corner of the frame. Usually these are the smallest panes in a square bay window, shown as 'A' in the diagram below. Measure to the nearest millimetre. This is your width measurement when ordering your blind.

  • Step 2

    If you have handles on your bay window you’ll need to account for how much they protrude. Measure out the distance your handle, air vent or any other obstruction extends out from the window frame. Make a note of this measurement, shown as ‘B’ below.

  • Step 3

    Add the depth of the handle or obstruction ‘B’ (if you have one) to the headrail depth of your chosen blind. Headrail depths can be found in the next table, and will form measurement ‘C’ below. Mark this location with a pencil. You should now have two pencil marks, one on the left of the bay window and one on the right. These are the starting and finishing points of the front window blind.

  • Blind Headrail Deductions

    When making the deductions for the headrail depth, please use the measurements below. 

    Blind TypeDeduction
    Aluminium 30mm
    Roman 50mm
    Top Fix Roller Blind 50mm
    35mm Wooden Blind 65mm
    50mm Wooden Blind 75mm
    Vertical Blind 75mm
  • Step 4

    Measure the distance between the two pencil marks you’ve just made, shown as ‘D’ in the diagram below. This measurement is the width of your new front window blind.

  • Step 5

    Now, measure the length of your windows. We recommend taking three measurements to ensure accuracy. Make note of the smallest measurement. This is the ‘drop’ measurement for ordering your blinds.

  • Step 6 - Let's order!

    Now you’ve got your measurements you’re ready to place your order. When ordering your blinds, we recommend selecting the ‘recess’ option. When this option is selected we will make a small deduction from the width to ensure a snug, yet easy fit.

    If you’d prefer to make a small deduction from the width yourself (we recommend 1.2cm) then do so and order your blinds as 'exact' size - depending on the product you’re ordering.

How to Measure for Bay Windows

Bay windows can look like a measuring challenge, but broken down into separate windows and with the right guidance, they're actually pretty straightforward. We've put together a guide showing you exactly how to measure for box angled bays and a box bay windows - so no matter what your window looks like, you'll be able to work out the sizes required for your blinds. If ordering samples we will include a bay window measuring guide for you so you can get the guides shown above and measure away in confidence.