How to measure windows for curtains and blinds

Accurate measurements are the one step you cannot skip before ordering curtains, blinds or a track. This guide covers the four measurements, the mistakes we see most often and a checklist to run before you send an enquiry.

Measuring a window for curtains in four steps

1. 1Width — Use a steel tape measure, not a tailor's tape, and measure three times: at the top, in the middle and at the bottom. Use the smallest figure. Even in a new building the width can vary by 5–10 mm.
2. 2Drop — Measure from where the track or pole will be fixed down to where the curtain should end: the floor, 1–2 cm above it, or the sill. Note which one you measured to.
3. 3Track length — Add 20–30 cm on each side of the window opening, so that open curtains clear the glass and let in as much daylight as possible.
4. 4Fabric width with fullness — Multiply the track length by the heading's fullness: 1.5× for an eyelet heading, 2.0× for a wave heading, 2.5× for a pinch pleat. Without it the folds look thin.

If you would rather have the windows measured for you, book a home visit: the designer measures every window, checks where the track can be fixed and brings fabric samples.

What you need

• —A steel tape measure (not a tailor's tape)
• —Paper and a pencil
• —A spirit level, if you have one, to check your lines
• —A second pair of hands for larger windows

Step 1: the width

Measure from one edge of the window frame to the other with a steel tape. Take three measurements, at the top, in the middle and at the bottom, and use the smallest: buildings settle, and even in a new home the width can vary by 5–10 mm. If the track or pole will sit above the window, add 20–30 cm on each side so that open curtains do not cover the glass.

Step 2: the drop

Measure from where the track or pole will be fixed (ceiling or wall) to where the curtain should end: the floor, 1–2 cm above it, or the sill. Write down exactly where you measured from and to; that decides later whether the curtain is too long or too short. A wall-fixed pole usually goes 10–15 cm above the window frame; a ceiling track makes the room look taller.

Step 3: the track length

The track should be 40–60 cm wider than the window opening, that is 20–30 cm on each side. Open curtains then hang better and let in more daylight. If the track is only as wide as the window, open curtains cover part of the glass and the room looks darker.

Step 4: the fabric width with fullness

Fabric width = track length × fullness. The fullness depends on the heading: 1.5× for an eyelet heading, 2.0× for a wave heading, and 2.5× for a pinch pleat. For example, with a 300 cm track and a wave heading the fabric width is 300 × 2.0 = 600 cm. Without enough fullness even an expensive fabric looks thin.

Checking your figures

1. 1Repeat every measurement at least twice
2. 2Measure the width and the drop in different places
3. 3Where the figures differ, use the smaller one

How wide should the curtains be?

For full folds, allow 1.5 to 2.5 times the track length in fabric. A lower fullness gives a flatter, minimal look; a higher one gives deeper folds. A wave heading is made at 2.0×, a flex tape and an eyelet heading at 1.5×, and a pinch pleat at 2.5×.

What to send us

• —The window width and height in centimetres
• —The track length you want, if you know it
• —A photo of the window taken from inside the room
• —A short note on how much privacy or darkness you want

Measuring for curtains, roller blinds and roman blinds

Not every window dressing is measured the same way. For curtains, the track length and the full drop from the fixing to the floor matter most. For roller and roman blinds, the width of the window or recess usually matters more, along with how far the sill projects, which way the window opens and where the handles are. That is why the same mistake costs different amounts: curtains may simply look less full, while a roller blind can stop the window from opening.

• —For curtains, measure the track length and the drop to the floor first.
• —For roller blinds, decide whether you are measuring the recess, the glazing bead or the whole frame.
• —For roman blinds, the width, the drop and where the mechanism will sit all matter.
• —For tracks and poles, also note whether the ceiling or wall is concrete, plasterboard or timber, because it decides the fixing.

A measuring template that prevents most mistakes

What works best is simple: one line, or one note on your phone, per window. Write down the room, the width, the drop, the product you have in mind, the fixing and anything in the way. That might be a radiator, the sill, a window handle, a low beam or a piece of furniture next to the window. These details are usually why a plan that works on paper fails in the room.

1. 1Room: living room, bedroom, kitchen or another space.
2. 2Width: at least two measurements if the opening looks uneven.
3. 3Drop: from the future fixing point to the floor or the sill.
4. 4Product: curtains, roller blinds, roman blinds or a track.
5. 5Notes: radiator, handle, depth, recess, sill, sloping ceiling.

When a measuring mistake costs the most

The costly mistake is rarely one centimetre; it is a wrong assumption. If you assume the track goes directly above the window and later decide it belongs at the ceiling, the whole drop changes. If you leave out the handle or the recess depth for a roller blind, it may not fit at all. And if you do not check that there is room for a roman blind's folded stack, the window can look heavy.

How do you check your measurements before sending them?

Before you send anything, run through a short checklist. Does every window have a room name? Do you know exactly where you measured from and to? Is it clear whether the curtain or blind hangs from the ceiling, the wall or the frame? Have you added at least one photo showing the whole wall around the window? These four questions catch most mistakes before the first conversation.

Measuring tall, corner and recessed windows

Tall, corner, floor-to-ceiling and recessed windows need more care, and one figure is not enough. Note whether the floor is level and whether a radiator, sill, side wall or furniture limits how the curtain can fall. For a corner window or several joined sections, decide early whether the track will run as one piece or in sections.

In a large room, do not measure only at eye level from a ladder. Ask someone to hold the other end of the tape: a few millimetres out at the top of a long drop shows at the floor. A photo with the measurements written on it also helps, because a few days later it is easy to forget which figure was from the recess and which from the fixing point.

Measuring before you have chosen curtains or blinds

If you have not yet decided between curtains, roller blinds and roman blinds, collect figures that work for all of them: the full width and height of the opening, the distance to the ceiling, the depth of the sill and roughly how much wall there is on each side. With those you can compare the options later without measuring again.

This is especially useful when you are redecorating in stages. You can check the budget first and then decide whether to go for curtains on a track or start with a more compact roller blind. Measuring more at the start gives you more choice and saves measuring everything again a week later.

When is a professional measurement worth it?

A professional measurement pays off when the windows are tall, in a corner, under a sloping roof or in a recess, or when one room combines several window dressings. Then the visit measures the whole set-up, not only the window: how much room the track needs, how the fabric will fall, where a roman blind's stack will end and whether a roller blind will catch on the handle. The more of these there are, the more one accurate visit is worth.

It also means you do not have to guess where to measure from and to. Measuring in the room also makes it easier to agree where the fixing looks best, how far the track should project and whether the curtains will cover a radiator, a sill or a door. That saves remaking things later.