Picture this: your beautiful new blinds arrive, you unwrap them with excitement, hang them up… and they’re two centimetres too short. The light gap at the top makes the room look unfinished, and now you’re stuck either living with it or starting all over again.
Here’s the truth nobody tells you — measuring your windows correctly is more important than choosing the fabric, the colour, or even the style of blind itself. Get this step wrong, and even the most beautiful blind in the world will look off.
The good news? It takes less than ten minutes, and once you know the rules, you’ll never get it wrong again.
First Things First: What Type of Window Do You Have?
Before you pick up a tape measure, you need to know what you’re working with. Different window types call for different mounting approaches, and getting this right from the start saves you a world of frustration.
Recessed windows sit inside a wall opening, with a visible frame or “reveal” around all four sides. These are the most common windows in homes and offer the most flexibility — you can fit blinds either inside the recess or outside it.
Flush windows sit almost level with the wall, with little to no recess. If your window doesn’t have a deep enough reveal (generally less than 6.5cm), an inside fit usually isn’t an option, and you’ll need to mount the blind outside the window frame instead.
Bay and bow windows are made up of multiple window sections set at angles, creating that lovely curved or angled alcove. These require either separate blinds for each pane or a continuous track system, and accurate measuring becomes even more critical because every angle can be slightly different.
French doors and large sliding doors often need blinds mounted outside the frame to allow full clearance for opening and closing — and you’ll want to factor in handle positions too.
Inside Fit vs. Outside Fit: The Decision That Changes Everything
This is the single most important decision you’ll make, because it determines exactly how you measure.
Inside fit (also called recess fit) means the blind sits within the window recess, against the frame. It gives you a sleek, built-in, minimalist look — the blind almost disappears into the window when not in use. This is the most popular choice for kitchens, bathrooms, and modern interiors where clean lines matter.
For an inside fit, you’ll need a window recess depth of at least 6.5–7.5cm (depending on the blind type) to allow the brackets and the blind itself to sit comfortably without obstruction from handles or hinges.
Outside fit (also called exact or face fit) means the blind is mounted on the wall or frame surrounding the window, covering the entire opening and a bit beyond. This is the better choice when you want to make a window appear larger, when the recess is too shallow, or when you simply prefer a more dramatic, statement look. Outside fit is also the safer option for windows that open inward, as it avoids any clash with handles.
How to Measure for an Inside Fit
- Width — Measure the width of the recess at the top, middle, and bottom of the window. Window recesses are rarely perfectly square (yes, even in newer homes), so always use the smallest of the three measurements. This ensures your blind will fit even at the tightest point.
- Height (Drop) — Measure the height of the recess from the top of the opening down to the windowsill, on the left, centre, and right sides. Again, use the smallest measurement.
- Depth Check — Measure how deep the recess is. You’ll need a minimum depth depending on the blind type (we recommend checking with us before ordering if you’re unsure), to ensure brackets, headrails, and the rolled-up blind itself have enough clearance.
- Watch for obstructions — Check for handles, locks, alarm sensors, or pipework that might interfere with the blind’s operation once installed.
How to Measure for an Outside Fit
- Width — Measure the width of the area you want the blind to cover, then add at least 7–10cm on each side (so 14–20cm total) for adequate light blockage and overlap. The more overlap, the better the privacy and light control.
- Height (Drop) — Measure from where you want the top of the blind to sit down to where you want it to end — whether that’s the windowsill, below the sill, or the floor for a more dramatic look. Add roughly 7–10cm above the window opening to ensure full coverage when the blind is lowered.
- Mounting surface — Confirm that the wall or frame around the window can support the fixings. Plasterboard, brick, and wood all require different fixing methods.
Top Tips for Measuring Like a Professional
Always use a steel tape measure rather than a fabric one — fabric tape can stretch slightly over time and throw off your measurements by a few millimetres, which matters more than you’d think.
Measure in centimetres, and always to one decimal place. The difference between 120.0cm and 120.5cm might not sound like much, but it can be the difference between a blind that fits perfectly and one that gaps at the edges.
Measure twice. It’s an old saying for a reason. Windows settle, walls shift slightly over time, and even small inaccuracies compound when you’re ordering custom blinds.
If you’re measuring multiple windows in the same room, don’t assume they’re identical — even windows that look the same size can vary by half a centimetre or more, especially in older properties.
When in Doubt, Let Us Help
Measuring for blinds doesn’t need to be intimidating, but we understand that getting it wrong can be costly and frustrating. That’s exactly why our team at Dekoris offers guidance every step of the way — from helping you decide between an inside and outside fit, to double-checking your measurements before your order goes into production.
After all, the perfect blind starts with the perfect measurement. Get in touch with us today, and let’s make sure your windows are dressed exactly the way they deserve to be.
