How to Measure for Curtains (2026)

Curtains are one of the easiest things to get wrong by a few centimetres and one of the most noticeable when you do. Order them off the window size instead of the track, or forget the fullness that makes them look gathered rather than flat, and the whole room looks slightly off. The good news is that curtain measuring follows a few clear rules. This guide walks through width, drop, fullness and the day-and-night layering common in Singapore homes, all in centimetres and inches.

First rule: measure the track, not the window

The single most common mistake is measuring the glass. Curtains hang from a track or rod, and their finished width is based on that rail, not the window opening. So the order is always: decide where the rail goes, fit or measure the rail, then size the curtains to it.

Use a metal tape measure and, for a wide living-room window, get a second person to hold the other end. Measure the full length of the track from end to end. If you are buying a new rail, size the rail first using the extension rule in the next section, then measure it.

Width: how far to extend past the window

A track that stops at the edge of the window forces the curtains to sit over the glass even when open, blocking light and looking cramped. Extend the track 15-20cm (6-8in) beyond each side of the window so the open curtains stack onto the wall and off the glass. On a wide window you can go a little further so the full pane is clear.

Also decide the height of the rail. Mounting it 10-15cm (4-6in) above the window frame, or higher toward the ceiling, makes the window look taller and the ceiling higher, which helps in compact HDB rooms. Just make sure the extra height still lets the curtain cover the top of the glass.

Drop: sill, below-sill or floor-length

The drop is the finished length from the top of the curtain to the hem. There are three standard choices:

• Sill length — the hem meets the windowsill. Neat for kitchens and windows with an aircon ledge, a bomb shelter or furniture below.
• Below-sill — about 10-15cm (4-6in) below the sill, a softer look that still clears low obstacles.
• Floor-length — the hem ends about 1-2cm (roughly half an inch) above the floor. The most elegant option for living and bedroom windows, but it needs a clear floor below.

Measure the drop from where the curtain hooks or rings sit, not from the top of the rail, because that is where the fabric actually begins. Measure at both ends of a wide window, as floors and ceilings are rarely perfectly level.

Fullness ratio: the secret to a gathered look

Curtains are meant to gather, not stretch flat across the window like a bedsheet. That gather comes from ordering more fabric width than the track. The fullness ratio is how much more:

For most homes, aim for 2 to 2.5 times the track width in total fabric across the pair. Sheer fabrics can take the higher end since they are light. If you buy ready-made panels, add the panel widths together and check they hit that multiple of your track.

Ceiling-mount versus wall-mount

Where you fix the track changes the look and what you can measure to. A wall-mounted rail sits above the window frame and is the usual choice. A ceiling-mounted track is fixed to the ceiling or into a false-ceiling recess, which makes curtains run floor-to-ceiling and the room feel taller, and it hides the rail neatly.

In HDB and condo units with a curtain recess or false ceiling built during renovation, ceiling-mount is common and worth planning for early. If you are coordinating this with other works, our lighting plan for a renovation guide covers how ceiling details get decided before the contractor closes them up. Whatever you choose, check the fixing surface is solid, not hollow plaster, and measure the recess width if there is one.

Day and night curtains: the Singapore layering

Given how bright and warm Singapore is, many homes hang two layers on a double track. A sheer day curtain sits nearest the glass; it cuts glare and gives daytime privacy while keeping the room bright. A night curtain, usually a dimout or blackout fabric, sits on the outer track to block light and streetlight for sleep.

Measure both layers to the same track logic, but note the two tracks sit a few centimetres apart, so the outer curtain needs a fractionally longer drop to reach the same hem line and clear the inner layer. If you are still weighing your options, our comparison of curtains versus blinds for HDB flats can help you decide before you measure. Once your window treatment is set, tie it into the rest of the room using our guide on how to measure a room for furniture.

Common mistakes and how to avoid them

A few errors come up again and again. Measuring the window instead of the track gives curtains that never quite cover the glass. Forgetting fullness leaves them flat and skimpy. Ordering one wide panel for a big window, when a pair that meets in the middle draws far more easily. And guessing the drop from the rail rather than from the hooks, which sits the hem a few centimetres off.

Two more are specific to our homes. Curtains that puddle on a humid floor can wick moisture and stay damp, so keep floor-length hems a clean 1-2cm clear rather than pooling. And on a window with an aircon ledge or bomb-shelter door below, a floor-length drop simply will not fit, so measure to a sill or below-sill length instead. When in doubt, measure twice and write both the track width and the drop on a labelled note before you order.

Putting the measurements together

To order a pair of curtains you need three numbers: the track width (rail length, already extended past the window), the drop (measured from the hooks to your chosen hem), and the fullness (track width times 2 to 2.5 for total fabric). Give the retailer or tailor all three and specify the heading type, since pinch-pleat, eyelet and tape headings gather differently. If in doubt, round the drop down a touch for floor-length so the hem never puddles, and keep a note of every figure for when you reorder for another room.

The bottom line

Good curtains come down to measuring the track rather than the window, extending it 15-20cm past each side, picking a drop that suits what sits below the sill, and ordering 2 to 2.5 times the track width in fabric so they gather properly. In Singapore, plan for a sheer day curtain and a dimout night curtain on a double track, and decide between wall and ceiling mounting before you fix anything. Get those numbers right and your curtains will hang full, cover the glass and frame the window the way they should.