Almost every curtain problem we get asked about traces back to a measurement taken in a hurry. Ten careful minutes with a steel tape saves a great deal of frustration later, so it is worth doing properly.
You will need a steel tape measure rather than a fabric one, a pencil, and ideally a second pair of hands for wider windows.
Step one: measure the window recess
Start with the window itself. Measure the width of the recess at the top, and note it down. This is your reference point, not your pole length — the pole will be wider.
Step two: work out your pole width
A curtain pole should extend beyond the window on both sides. This is called the overhang, and it exists for a practical reason: when the curtains are open, you want them stacking against the wall rather than covering the glass. That extra width lets more daylight into the room and makes the window look larger.
As a general rule, allow 15–20cm of overhang on each side. So a 140cm window recess suits a pole of roughly 170–180cm.
Two things can change that. If you have heavy or interlined curtains, the fabric stack is deeper, so lean towards 25cm each side. If a wall, radiator or door frame limits the space, work with what you have — an uneven overhang looks worse than a modest one, so keep both sides equal even if that means less than ideal.
Step three: decide the height
Position the pole 10–15cm above the top of the window recess. Higher draws the eye upward and makes the ceiling feel taller, which is why designers often go higher still in rooms with generous ceiling height.
Check two things before committing. First, that you have solid wall to fix into above the window — plasterboard alone will not hold a loaded pole. Second, that the brackets will clear any window opening mechanism, blind fitting or coving.
Step four: measure the drop
The drop is measured from the eye of the curtain ring, not the pole itself, down to where you want the curtains to finish. This catches people out regularly: measuring from the pole gives you curtains 3–4cm too long.
Where curtains should finish depends on the look you want:
- Sill length — finishing about 1cm above the sill. Practical for kitchens and bathrooms, or where a radiator sits below the window.
- Below sill — roughly 15cm below the sill. A useful middle ground.
- Floor length — finishing 1cm above the floor. The most common choice in living and dining rooms. That 1cm gap keeps the hem clean and lets the curtains draw freely.
- Puddled — 5–10cm longer than floor length, so the fabric gathers on the floor. A softer, more traditional look, though less practical in a busy room.
Step five: choose your pole diameter
Diameter is a question of weight and proportion, not just looks. A 19mm pole suits lightweight curtains on a narrow window. 28mm is the workhorse size and handles most domestic windows comfortably. For wide spans or heavy interlined curtains, 35mm or larger gives the strength you need and looks properly in scale.
Longer poles need a centre bracket to prevent sagging. As a guide, anything over about 200cm should have one, and over 300cm you may want two.
A few things people forget
Measure each window individually, even in a room where they look identical — older houses are rarely square, and a 2cm difference is common.
If your curtains are already made, measure them before ordering the pole rather than the other way round.
And note the finial length. Finials sit beyond the pole ends, so a pole described as 180cm may occupy 195cm of wall once the finials are on. If space is tight, check the total fitted width rather than the pole length alone.
Still unsure?
Awkward windows — deep recesses, bays, sloping ceilings, windows close to a corner — are worth a second opinion before you order. Send us your measurements and a photo and we will tell you what will work.