How to Position Curtain Rails and Curtains to Make a Room Look Bigger

We all know that odd feeling when we walk into the living room: everything is clean, the sofa is positioned properly, the cushions are doing their job… yet the room somehow feels cramped. Often, the culprit is hiding just above the window. A curtain rail fitted too low divides the wall in two and, almost imperceptibly, makes the whole room look smaller. I have seen this one detail turn a compact one-bedroom flat into a brighter space in under an hour, simply by raising the curtains by a few centimetres. It is neither magic nor an extravagant expense. It is all about the eyeline. And interior designers have a very clear rule on the matter.

The professionals’ rule: fit the curtain rail close to the ceiling

In any interior, the eye naturally follows vertical lines. When a curtain rail is installed immediately above the window, as was often done in the past, it instantly reveals the wall’s true height and makes the ceiling seem lower. Professionals instead favour placing the curtain rail 10 to 20 centimetres below the ceiling, or immediately beneath a cornice where one is present. The gaze is drawn upwards, the window appears larger and the room finally feels more open. It is a modest adjustment, but the visual transformation can be genuinely striking.

In a 12 m² bedroom with a 2.50-metre ceiling, a rail installed 15 centimetres above the window can leave 35 or 40 centimetres of unused wall above it. Raising the fitting to 5 centimetres below the ceiling brings that height into the scheme. The window can look almost a third larger, even though the glazing has not moved by a millimetre. One interior decorator often puts it humorously: “Curtains do not alter the walls, but they are very good at telling them a more flattering story.”

The effect comes from a fairly straightforward principle: a high horizontal line visually lengthens the wall surface, while a low one cuts across it. Curtains act as a vertical frame, particularly when they fall in a straight line to the floor. The brain first registers the upward flow of the fabric before it truly judges the room’s height. In period homes, where ceilings are generously proportioned, this approach highlights the existing volume. In newer homes, it helps disguise a few missing centimetres. This is why professionals nearly always avoid fitting a rail level with the window frame.

The right curtain rail height for your ceiling and window

The guideline is simple: position the rail 5 centimetres below the ceiling in a low room, or between 10 and 15 centimetres beneath it if you have more height and no mouldings to accommodate. Where there is a cornice, fit it directly underneath so that this attractive architectural feature remains on display. If the ceiling is particularly high, there is no need to lower the rail to “fill” the wall: keep it high, but opt for curtains with enough substance that they do not look lost. The point is not to obey one fixed measurement, but to extend the wall upwards.

The other game-changing detail lies at the sides. The curtain rail should extend 15 to 25 centimetres beyond each side of the window frame, or even further if the wall allows it. When the curtains are open, the panels barely cover the glass and daylight can properly enter the room. Many people still buy a rail exactly the same width as their window, either from habit or to save a few pounds. That is understandable, but it makes the opening appear narrower. Let us be honest: nobody measures this every morning, but you immediately sense when a window finally seems able to breathe.

To achieve the look without getting it wrong, keep three measurements in mind before drilling into the wall:

“A well-positioned curtain rail should make the window seem larger than it really is, without drawing attention to itself.”

• Position it 5 to 20 cm below the ceiling, depending on whether there is a cornice.
• Extend it 15 to 25 cm beyond each side of the window.
• Select a length that skims the floor or ends roughly 1 cm above it.

The final point deserves its place on the list: curtains that are too short spoil the vertical effect, even if the curtain rail has been fitted perfectly.

Floor-length curtains: the finishing touch that makes a room feel bigger

Once the curtain rail has been raised, the fabric length determines whether the illusion feels convincing. Ideally, curtains should finish 1 centimetre above the floor, or just lightly touch it in a room with little foot traffic. Fabric hovering 10 or 15 centimetres above a wooden floor looks temporary, as though you are still waiting for the removal van. Conversely, a slight break on the floor can look charming in a romantic bedroom or traditional living room, but it soon gathers dust. For a busy everyday home, a clean drop is the better choice: elegant, practical and less demanding.

Fabric matters too, though there is no need to turn your living room into a showroom. Full, light-coloured sheer curtains allow daylight through while creating the desired long vertical line. In a dark room, avoid overly heavy fabrics hung on a slim rail: the contrast may make the window feel harsher rather than opening it up. Shades close to the wall colour work especially well because they soften visual breaks. Beige against a sand-coloured wall, off-white against warm paint, or soft grey against a mineral-toned wall will extend the scheme very naturally.

There is one exception: beneath a window, there may be a radiator, a wall-mounted desk or a window seat used every day. In that situation, full-length curtains are not always practical, and there is no reason to feel guilty about it. Choose a blind fitted high instead, combined with decorative side panels that reach the floor without obstructing how the room is used. The eye will still travel towards the ceiling. This is especially useful in small bedrooms and kitchens, where every centimetre has a purpose. Visual coherence matters more than applying a rule blindly.

The real luxury is not the size of the room, but how you see it

Moving a curtain rail may seem insignificant beside more dramatic renovation work, yet it is often one of the most cost-effective changes in decorating. It requires neither knocking down a partition wall nor replacing the windows, only a tape measure, a spirit level and a little confidence. Before drilling, you can even test the idea with masking tape: mark the proposed position, step back a few paces, then see what the room tells you. You may find that the ceiling you thought was unremarkable had simply not been presented to its best advantage. A better-framed window also brings in more light and can make you want to clear the sill, move a plant or let the room breathe. Good curtains are not merely an accessory: they change the way you live in a space.

Key point	Detail	Benefit for the reader
Curtain rail height	Position it 5 cm below the ceiling in a low room, or up to 10 or 20 cm beneath the ceiling depending on the layout.	The eye is drawn upwards and the ceiling instantly appears higher.
Curtain rail width	Allow the rail to extend 15 to 25 cm beyond each side of the window frame.	Curtains clear more of the glass, making the window look wider.
Panel length	The curtain hem should skim the floor, ideally ending around 1 cm above it.	The vertical line remains unbroken and the room-enlarging effect is strengthened.