How to Measure for Roller Blinds Properly

A roller blind can look spot on or slightly off, and the difference usually comes down to a tape measure. If you are wondering how to measure for roller blinds, the good news is that it is straightforward once you know whether your blind is going inside the recess or outside it.

Getting the measurements right matters for more than appearance. A made-to-measure blind should sit neatly, roll smoothly and give you the level of privacy and light control you actually want. Measure badly and you can end up with gaps at the sides, a blind that catches on handles, or one that simply does not cover enough of the window.

Before you measure for roller blinds

Start with a metal tape measure rather than a cloth one. Cloth tapes can flex and give less reliable numbers, especially across wider windows. Measure in millimetres, not centimetres, and write each measurement down as you go. That avoids rounding and gives a much more accurate fit.

It also helps to decide what sort of fit you want before you take a single measurement. For roller blinds, that usually means choosing between an inside recess fit and an outside recess fit. An inside recess fit sits within the window opening for a clean, tidy finish. An outside recess fit sits above or around the opening and is often better if you want to block more light or cover a window that has little depth inside the recess.

If your window has tiles, a deep sill, protruding handles or vents, check those first. These details can affect how the blind hangs and how much clearance you need.

How to measure for roller blinds inside the recess

An inside recess blind is the usual choice when you want a fitted look. The blind sits within the window opening rather than overlapping it.

To measure properly, take the width in three places - across the top, middle and bottom of the recess. Recesses are not always perfectly square, especially in older properties, so this step matters. Use the narrowest of the three width measurements.

Then measure the drop in three places - left, centre and right. Use the longest drop measurement so the blind has enough length to cover the full opening.

If the supplier asks for recess size, give the exact recess measurements and let them make any allowances needed for the blind mechanism. If they ask for exact blind size, follow their measuring instructions carefully because roller blinds include brackets and controls, and the fabric width is usually narrower than the full blind width.

This is where people often come unstuck. They assume the ordered width equals the fabric width, but with roller blinds the complete blind size includes the operating mechanism. That means the fabric itself will usually be slightly narrower, leaving a small light gap at each side. That is normal, but it is worth knowing if you are fitting blinds in a bedroom or nursery where blackout performance matters.

Check recess depth before ordering

Depth is easy to overlook, but it can decide whether an inside recess fit is practical. If the recess is too shallow, the brackets or blind tube may project awkwardly, or the blind may catch on handles.

Measure from the front edge of the recess to the glass or any obstruction. Then compare that with the minimum depth needed for the blind you want. If your window handle sticks out a long way, an inside fit may still work, but the blind might need to sit further forward within the recess. In some cases, an outside recess fit is simply the better option.

How to measure for roller blinds outside the recess

If you want to make the window look larger, cover an awkward opening or reduce light gaps, measuring outside the recess is often the right move. This is especially useful for blackout roller blinds, because fitting beyond the recess helps block more light at the edges.

For the width, measure the area you want the blind to cover, not just the glass or opening. A common approach is to add at least 70mm to 100mm on each side of the recess, where space allows. That extra overlap helps with privacy and light control.

For the drop, measure from where the top of the blind will be fixed down to where you want it to finish. Many people mount the blind 70mm to 100mm above the recess so it clears the opening neatly and gives better coverage when lowered. If the blind will hang over a sill, decide whether you want it to stop at the sill or continue below it.

There is no single perfect allowance for every window. It depends on the wall space available, the look you want and whether there are obstructions nearby such as radiators, shelves or light switches.

Think about handles and obstacles

An outside recess blind needs enough stand-off from the wall to hang freely. If the window has projecting handles, measure how far they come out. The blind should clear them comfortably when lowered.

This matters in kitchens and bathrooms, where tilt-and-turn windows or chunky handles are common. If there is not enough clearance with a standard fitting, check whether extension brackets are available.

Common measuring mistakes to avoid

Most sizing problems come from a few very fixable errors. The first is measuring only once. Always measure width and drop in three places where relevant, because walls and recesses are rarely perfectly even.

The second is mixing up recess size and blind size. If a made-to-measure supplier asks for recess measurements, do not make deductions yourself. If you trim numbers down on your own and the manufacturer also makes allowances, the blind can end up too small.

The third is forgetting the control side, chain drop or bracket space. On most roller blinds, the mechanism adds to the overall width. That is normal, but it means tight spaces need a little more thought.

Another common issue is ignoring the fabric gap at the sides. If you need the darkest possible room, standard roller blinds will usually let in some light at the edges. You can reduce that with an outside recess fit, more overlap, or by choosing a blind position that gives the best coverage for the window.

Measuring tricky windows

Not every window is a simple rectangle with plenty of clear wall around it. Bay windows, tiled bathroom recesses and windows close to adjacent walls all need a bit more care.

For a bay, measure each section separately and check how much room there is for brackets and controls. You may need to think about where chains will sit so blinds do not interfere with each other.

For tiled recesses, measure tile to tile and check whether the surface is even enough for fixing. In bathrooms, waterproof and wipe-clean options are often the practical choice, but they still need accurate sizing.

For windows tight to one side wall, look at the bracket clearance and how the blind will operate. Sometimes a recess fit works better simply because the outside wall space is limited.

What to have ready before you order

Once you have your measurements, check them again before placing an order. It helps to note whether each blind is recess or outside recess, which room it is for, and whether there are any handles or obstacles that affect the fit.

If you are ordering more than one blind, label each set of measurements clearly. Bedroom front window, kitchen side window and bathroom small window is much easier to follow than a page of loose figures with no explanation.

This is also the point to think about fabric choice. Blackout blinds are a strong option for bedrooms, while PVC waterproof blinds make more sense in bathrooms and kitchens where moisture and wipe-clean practicality matter more. The measurement method stays much the same, but the room use should shape the product you pick.

If you want extra reassurance, sample fabrics can help you narrow down colour and finish before ordering. That way you are not only confident about the size, but also about how the blind will look in the space.

When it is worth measuring twice

If the window is unusually wide, the recess is clearly uneven or the blind is for a room where light control really matters, measure again on a different day. That might sound excessive, but it is cheaper than replacing a made-to-measure blind.

The same goes for rental properties or replacement jobs where you are updating several windows at once. A few extra minutes with the tape measure can save a lot of hassle later, especially if you are trying to keep costs down while still getting a neat, made-to-measure result.

For straightforward online ordering, the best approach is simple: decide the fit first, measure carefully in millimetres, and do not second-guess the deductions if the retailer makes them for you. If you need made-to-measure options with practical choices for blackout, waterproof and everyday rooms, Queen Blinds keeps the process clear. A careful measure now makes the whole job easier when the blind arrives.