How to Measure Bay Window Blinds

Bay windows look great until it is time to measure them. That is usually the point where people realise this is not one wide window, but three or more sections meeting at angles, with little room for guesswork. If you are wondering how to measure bay window blinds, the good news is that it is straightforward once you break the job into individual window faces and measure each one properly.

The main thing to remember is this: a bay window is never measured as one full span if you want separate blinds that fit neatly. Each pane or section needs its own width and drop, and the exact method depends on whether your blinds will sit inside the recess or outside it. Get that part right, and ordering made-to-measure blinds becomes much easier.

How to measure bay window blinds the right way

Start by deciding how the blinds will be fitted. In most bay windows, blinds are fitted as separate units, one for each section of glass. That gives you better control over light and privacy, and it usually works best with roller blinds, vertical blinds and many blackout options.

Before you measure, you will need a metal tape measure, something to write the sizes down with, and a step stool if the top of the recess is high. Avoid using a fabric tape measure because it can stretch and throw the numbers off.

Measure in millimetres, not centimetres. That removes confusion and gives a cleaner made-to-measure result. Also, measure each section yourself even if the windows look identical. In bay windows, they often are not.

First, identify each section of the bay

Treat the bay as separate window faces. A standard angled bay may have a left window, a centre window and a right window. Larger bays can have more sections. Label them as you go, such as left, centre and right, so you do not mix up your figures later.

This matters because even a few millimetres difference can affect how neatly the blinds sit, especially where the frames meet at the corners.

Measuring inside the recess

If the blinds are going inside each window recess, measure the width of every section in three places - top, middle and bottom. Use the narrowest width. Then measure the drop in three places - left, centre and right - and use the shortest drop.

That method allows for slight unevenness in plaster, timber or uPVC frames. Bay windows often look square but have small variations, and those small variations matter when you are ordering custom blinds.

For recess fitting, do not make your own deductions unless the supplier specifically asks you to. Made-to-measure blinds are usually adjusted for fitting during production. Sending the true recess size is normally the safest option.

Check for handles, vents and tight corners

This is where bay windows can catch people out. If your window has handles that stick out, trickle vents at the top, or shallow recesses, the blind might not hang freely even if the width is technically correct.

Look at the depth of the recess as well as the face width. A roller blind, for example, may need enough depth for the bracket and the roll itself. In tighter bays, there can also be limited clearance near the angled joins, which affects whether blinds sit neatly side by side.

If space is tight, it may be better to fit the blinds outside the recess instead. That gives more room, but it changes how you measure.

Measuring outside the recess

If you are fitting blinds outside the recess, measure the exact area you want each blind to cover rather than the window opening itself. In most cases, that means adding extra width and extra drop so the blind overlaps the frame and blocks more light.

A common approach is to add around 50mm to 100mm to the width and drop, depending on the space available. The right amount depends on your wall space, the shape of the bay and whether the blinds might clash at the corners.

With bay windows, this is the part where practical judgement matters. Too much overlap can make adjacent blinds knock into each other or look crowded. Too little can leave gaps. If the sections sit close together at an angle, a modest overlap often works better than a generous one.

Think about how the blinds will operate

When measuring outside the recess, consider the chain side, stack, or roll position of the blind. On a bay, neighbouring blinds need enough room to operate without catching each other. This is especially relevant with roller blinds in tighter angled bays.

It also helps to think about how often you will open them. In a living room bay, you may want a clean fit that looks tidy from outside. In a bedroom, blackout performance may matter more, so a slightly wider overlap can be worth it.

Measuring angled bay windows

Most people searching for how to measure bay window blinds are dealing with an angled bay rather than a curved one. In an angled bay, you do not need to measure the corner angles with most standard blind types if each blind is fitted separately to its own section. What matters most is the width, drop and available fitting space for each individual blind.

That said, corner clearance still matters. The closer the blinds are to the angled joins, the more important it is to check bracket space and blind movement. If one section has a much shallower recess than the others, you may need to alter the fitting type for that section or choose a blind style that works better in tighter spaces.

Vertical blinds can be useful for wider bay sections because they offer flexible light control and are practical in living spaces. Roller blinds are often the simple choice for a neat, modern look. Blackout fabrics work well in bedrooms, but they need careful measuring if light gaps are a concern.

What to avoid when measuring bay window blinds

The biggest mistake is measuring the whole bay as one width when you actually need separate blinds. That nearly always leads to a poor fit. The next most common issue is assuming all sections are the same size. Measure every one.

Another problem is ignoring obstructions. Window handles, alarm sensors, tiles, projecting sills and vents can all affect the fit. If the blind cannot hang straight or the bracket cannot sit flat, the measurements alone will not save the order.

It is also worth rechecking every number before you buy. Bay windows are awkward enough without having to reorder because a 1360 was written down as 1630.

A simple measuring example

Say your bay has three sections. You measure the left recess width at 620mm, 618mm and 619mm. You would use 618mm. Then you measure the drop at 1200mm, 1198mm and 1199mm. You would use 1198mm.

Repeat that process for the centre and right sections and record them clearly. You may end up with three slightly different sizes, and that is completely normal. In fact, it is a good sign that you have measured properly rather than guessed.

When it depends on the blind type

Not all bay window blinds are measured in exactly the same way once fittings are considered. Roller blinds are generally straightforward, but you still need to account for bracket position and fabric gap. Vertical blinds may need more thought around headrail placement and vane clearance. If you are replacing only worn slats or an existing track, you may need to measure the current components rather than the full recess.

This is where buying made-to-measure helps. You are not trying to force a standard blind into an awkward bay. You are ordering for the actual size of your window, which usually looks better and wastes less time than trial and error with off-the-shelf options.

For practical households, rented homes and quick refresh jobs, that matters. A proper fit looks cleaner, works better and saves dealing with blinds that sit crooked or leave obvious gaps.

Final checks before you order

Once all sections are measured, go back and check each figure one more time. Confirm whether the sizes are recess or exact blind sizes, note which window each set belongs to, and make sure the measurements are in millimetres.

If your bay is especially tight, has unusual angles or includes obstacles, take a moment to think beyond the numbers. The best blind is not just the one that matches the measurement. It is the one that fits the space, clears the handles and does the job you need, whether that is blackout, privacy or an easy-clean finish. If you want a simple route, Queen Blinds offers made-to-measure options that take the guesswork out once your sizes are right.

Measure carefully, write everything down clearly, and do not rush the awkward corners. Bay windows are a bit more involved, but once you treat each section as its own window, the whole job becomes much easier.