How to Measure for a Ceiling-Fixed Bay Window Curtain Track
For floor-length curtains hanging in front of the window sill
If you’re planning floor-length curtains that hang down in front of your bay window sill, the measuring position changes slightly.
This guide shows you exactly where to measure from and what sizes we need. Don’t worry if your bay window isn’t exactly the same shape as the examples below — the measuring method is the same for most bays.
Is this the right guide for you?
This page is for you if:
- your curtain track will be ceiling-fixed
- your curtains will hang in front of the bay
- your curtains will be floor-length
If your curtains will stop at the sill and stay within the bay, you’ll want the sill-length guide instead.
Where to measure from
The key difference with this setup is:
You measure from the front edge of the window sill — not the back.
This is because your curtains will hang down in front of the sill rather than inside the bay.
So instead of following the window frames, you follow the line where the curtains will actually hang.
Measure from the front edge of the sill — not the back
You can also measure from the walls under the window sill.
Important: how deep is your window sill?
This part is really important and affects how your curtains will sit.
If your sill is shallow and stays within the bay shape, then you can measure as shown above and your curtains will sit neatly in front.
If your sill is deep and projects out beyond the bay, you may end up with gaps at the sides where the curtains don’t fully close.
If that applies to your bay, take a look at this guide which explains how to deal with that properly:
Different bay shapes, same measuring method
Every bay window is slightly different, but the measuring method is the same.
You are measuring the shape where the curtains will hang — not just the window itself.
How to measure your bay window in 3 simple steps
Once you know where to measure from, the process is straightforward.
Step 1: Measure each section along the front edge
Measure each straight section following the front edge of the sill.
If you measure from the walls under the sill. Then also let us know how much the sill sticks out.
Step 2: Measure across the front of the bay
Measure across the full width of the bay at the front position.
This size is from the corner of bay on one side to the other
Step 3: Measure the diagonals
The diagonal measurements allow us to calculate the angles correctly.
If you measured from under the sill. Then measure the diagonals from under the sill as well
It’s simpler than it looks
Once you understand where to measure from, the process becomes very straightforward.
Take your time, measure in centimetres, and write each size down as you go.
Want to make it even easier?
You can use one of our printable measuring templates to guide you.
Example: 5 sided bay measuring template
Fill it in as you go, then either upload a photo or enter the sizes manually when ordering.
Still unsure? Just ask
If you’re unsure about anything, send a photo and I’ll take a look.