How to measure a bay window for curtains
Bay windows are the most rewarding window to dress and the easiest to get wrong. This is the way we'd measure one: the same method we use before specifying a pole or track for a client's project.
A bay window earns its keep: it floods a room with light and gives a flat wall a sense of depth. But that same shape (two, three or more faces meeting at angles) is exactly what makes it unforgiving to measure. Get the angles or the drop wrong and even the finest hardware will hang badly. The good news: measure it methodically and a bay is no harder than a flat window. Here's how.
First, identify the type of bay
Before you reach for the tape, work out which kind of bay you're dressing, because it decides how the hardware bends or joints.
Square bay
Faces meet at 90°, with a flat front and square returns. Crisp right angles to measure and bend around.
Splayed bay
Angled, shallower corners, often 135°, with three or more faces. The most common bay, and gentle to curve.
Box / bow bay
A long flat front with short returns, or a continuous curve. Needs careful bending to follow the sweep.
Measure each face separately
Don't try to measure a bay as one number. With a steel tape, measure the width of every face in turn: left return, front (or fronts), right return: along the exact line where the pole or track will sit, which is usually 12 to 15cm above the frame. Write each face down separately. The hardware is made up from these individual measurements, not from a single span across the opening.
Note the angle at every corner
This is the step that separates a bay that works from one that fights the window. At each internal corner, note the angle: 90° for a square bay, shallower for a splayed one. A track is bent to these angles; a pole is jointed with corner connectors cut to them. Get the angles right and the curtain runs the whole bay; get them wrong and it snags at every corner.
Measuring the faces but guessing the angles, then the bent track or jointed pole doesn't sit flush to the wall at the corners. The angle is a measurement, not an estimate. If in doubt, a simple paper template pressed into the corner captures it exactly.
Measure the drop in three places
Measure from where the curtain will hang (the ring or glider) down to the desired hem. Do this in three places across the bay: and use the shortest, because bay floors and sills are rarely level. A floor-length curtain in a bay should clear the floor by around 1cm so it doesn't catch as it draws around the angles.
Allow for stack-back and clearance
Curtains still need somewhere to go when open, ideally onto the short returns or the wall beside the bay, not across the glass. Add a stack-back allowance at the ends, and check the bay's particular obstructions: a window seat, a radiator, deep sills or handles, and the ceiling line where the bay meets the room. Our stack-back and clearance guide covers the allowances in full.
Pole or track for a bay?
For most bays a track is the easier, cleaner answer: it bends to follow the angles and lets the curtain draw smoothly around the whole window. A pole can be jointed around a bay with corner connectors where the hardware is meant to be seen, but note that standard eyelet curtains can't pass the corner brackets. Our pole-or-track guide and heading styles guide help you decide before you order.
Common questions
Should I use a pole or a track in a bay window?
Both work, but a track has the edge: it bends to follow the angles for a continuous, smooth run, and suits most headings. A bay pole can be jointed around the corners with connectors but reads as a series of straights, and standard eyelet curtains cannot pass its brackets. Choose a pole when the hardware is meant to be seen and the heading suits it; choose a track for the cleanest run.
Can curtains cross the corners of a bay?
On a track, gliders pass smoothly around gentle bends so a curtain can draw across the whole bay. On a pole, rings cannot pass the corner brackets, so curtains are usually drawn to the sides or dressed as separate curtains on each face. Decide the draw before you specify.
Why does the bay type matter?
A square bay turns at 90 degrees, a splayed bay at shallower angles, and a box bay has a flat front with short returns. The angles decide how a track is bent or a pole is jointed, and which brackets are needed, so identifying the type is the first measurement, before any numbers.
How do I measure the drop in a bay?
Measure from where the curtain hangs (the ring or glider) down to the desired hem, in three places across the bay, and use the shortest. Floors and sills in a bay are rarely level, and the shortest drop stops the curtain catching at one end.