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Practical Guides

# How to Measure Windows for Curtains

Measuring is not difficult, but it is unforgiving. Here is the method we use, and the five errors we are most often called out to fix.

Written by Blessing Sefah Curtains & Blinds Deco
Published 11 August 2026
Reading time 6 min read
Category Practical Guides

We always measure on site before making anything, because the responsibility for a wrong fit should sit with us rather than with you. But it is genuinely useful to be able to take a rough measurement yourself — for budgeting, for comparing quotes, or for telling us what we are dealing with before a visit.

This is the method, in the order it should be done.

## What you need

- A steel tape measure. Not a fabric tape — they stretch, and over a 2.5m drop that matters.
- A step ladder, so you can measure the top of the opening directly instead of estimating.
- A pencil and paper. Record every window separately, even if they look identical.

Measure in centimetres and write down which window each figure belongs to. Two windows in the same wall are frequently 1–2cm different.

## Step 1: decide the track position

This comes first, because both the width and the drop are measured from the track — not from the window. Decide whether the track will be:

- Wall-fixed above the frame — typically 10–15cm above the opening, or higher if the ceiling allows.
- Ceiling-fixed or concealed — set into or just below the slab, for a full-height line.
- Inside the reveal — only where the reveal is deep enough and a blind is not being used.

Check what is actually above the window before committing. Concrete lintels, service runs and curtain boxes all change what is possible.

## Step 2: measure the width

Measure the track or pole width, not the window width. The track should extend past the opening on both sides so the curtains can stack clear of the glass:

- Add 15–20cm each side as a normal allowance
- Add more — up to 25–30cm — for heavy, lined curtains, which stack thicker
- Check there is clear wall on both sides. A corner or a door frame limits how far you can go.

Write this figure down as the track width. Everything else is calculated from it.

## Step 3: measure the drop

Measure from the top of the track — or, for a pole, from the bottom of the ring where the hook will sit — down to where you want the hem to finish. Then:

- Floor length: deduct about 1cm so the hem clears the floor
- Break length: add 2–4cm for a soft fold on the floor
- Sill length: finish about 1cm above the sill
- Below sill: finish 10–15cm below the sill

Measure the drop at both ends of the window and in the middle. Floors are rarely level, and if the three figures differ, the longest one is usually the number to work to.

## Step 4: work out the fabric width

Fullness is the ratio of finished fabric width to track width. It is what makes a closed curtain look generous instead of stretched:

- 2x — the standard for most curtains. A 200cm track needs about 400cm of finished fabric width.
- 2.5x — for lighter fabrics and sheers, which need more gather to read as full.
- 1.5x — the practical minimum, and only for very heavy fabrics or where stack space is genuinely limited.

Split that total across two curtains for a pair. Note that this is finished width — the cut width is larger, because fabric is consumed by hems, side turnings and pattern matching.

## The five common mistakes

1. Measuring the window instead of the track. The most frequent error, and it produces curtains that cannot cover the opening.
2. Measuring to an unfinished floor. If tiling or flooring is still to be laid, the drop will be too long by exactly the thickness of the finish.
3. Using one measurement for several windows. Openings that look identical usually are not.
4. Forgetting the stack. Without side allowance, open curtains sit over the glass and the room loses light.
5. Ignoring what is above the window. A track cannot be fixed where there is nothing solid to fix it to.

If you would rather not do this at all, that is entirely reasonable — measuring is part of our service. Send us the rooms involved and we will arrange a visit.

Next step

## Talk it through with our design team

Send us a photo of the window and we will suggest a shortlist that suits the room, the light and your budget.

Request a Quote Message Us
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