How to Measure Bay Window Angle for a Curtain Pole or Blind
Short answer: to measure a bay window angle, sit a digital angle finder into each internal corner and read the degrees directly. Most bays are either square, about 90 degrees, or splayed, about 135 degrees, but older homes are often a few degrees off — and that exact number is what a made-to-measure curtain pole or blind supplier asks for. The LEXIVON Aluminum Digital Angle Finder (£33.19) reads and holds the angle so you can note it and photograph it for your order.
Square or splayed? What bay angles usually are
A box or square bay has corners at about 90 degrees. A splayed bay sits at about 135 degrees, which is a 45 degree bend away from a straight run. Those are the common shapes, but the side walls of an older bay are frequently a degree or two off and are not always equal to each other — which is exactly why you measure rather than assume.
How to measure the angle, step by step
- At each internal corner, open the two arms so they lie flat against both walls
- Read the angle on the display and press hold, then write it down
- Measure each corner separately — do not assume the two sides match
- Measure the length of each wall section with a tape as well
Take a photo of the locked display against the corner; it is reassuring to have when you fill in the order form.
What suppliers need and why
Made-to-measure bay poles and bendable tracks are shaped to your exact corner angle, so suppliers ask for the corner degrees plus the wall lengths. Curtain-pole guides themselves recommend a protractor or a digital angle finder for this. Get the angle wrong and the pole will not sit right, which means a slow and costly re-order.
No angle tool at home? Options and their limits
A printed protractor traced onto cardboard is fiddly to hold in a corner and easy to misread; a phone app gives only a rough idea. A digital angle finder reads the inside corner directly and holds the number, so you can note it and photograph it with confidence. Afterwards the same tool is handy for blinds, shelves and hanging pictures level.
The LEXIVON is a 10-inch/250mm aluminium finder, £33.19 inc VAT, with free UK delivery and a 30-day returns window if you only need it once.
New to angle tools generally? Start with our digital angle finder UK guide.
Frequently asked questions
What angle is a bay window?
Most bay windows are either square, at about 90 degrees, or splayed, at about 135 degrees, which is a 45 degree bend from a straight line. Older homes are often a few degrees off, so it is best to measure each corner.
How do I measure a bay window angle for a curtain pole?
Open a digital angle finder into each internal corner so both arms sit flat against the walls, read the angle on the display and note it. Measure each corner separately and record the wall lengths too.
Why does a curtain pole supplier need the bay angle?
Made-to-measure bay poles and blinds are bent to your exact corner angle. An accurate figure means the pole fits first time, while a guess can lead to a pole that will not sit correctly.
Do I need a special tool to measure a bay window?
A digital angle finder is the simplest tool because it reads the inside corner directly and holds the number. The LEXIVON is £33.19 with free UK delivery and a 30-day returns window.
Measure once, cut once.
See the LEXIVON Aluminum Digital Angle Finder — £33.19 inc VAT, free UK delivery, 30-day returns and a 12-month warranty with UK support.