How to measure your windows for curtains

Most curtain disappointments are not fabric problems. They are measurement problems — a panel that stops short of the floor, or a rod too narrow so the curtain never really opens.

Here is the whole job in three numbers.

What you need

A metal tape measure, not a cloth one. A cloth tape sags and gives you a longer number than the truth. A pencil and paper, and someone to hold the other end if the window is wide.

1. Width

Measure the rod, not the window. Curtains hang from the rod, so the rod is what decides how wide the fabric has to be.

If the rod is not up yet, measure the window frame and add 15 to 20 cm on each side. That extra lets the curtain sit clear of the glass when it is open, so you get the full daylight instead of half of it.

Now multiply. For a gathered look you want two to two and a half times the rod width in fabric. A 150 cm rod needs 300 to 375 cm of curtain across it. Sheers can take more; heavy blackout usually looks better nearer two.

2. Height

Measure from the rod down to where you want the curtain to stop. Three common stopping points:

• Sill — just above the window sill, usual for a kitchen or a bathroom
• Below sill — about 15 cm under the sill, tidy for a small room
• Floor — 1 cm above the floor so it does not drag and collect dust

Measure at both ends of a wide window. Floors and ceilings in most homes are not perfectly level, and a centimetre of difference shows.

3. Quantity

Count the panels. Two panels that meet in the middle read better on most windows than one wide one, and they are easier to pull.

The two mistakes

Measuring the glass instead of the rod. The curtain then sits inside the frame and the room looks smaller than it is.

Rounding down. A curtain 2 cm too long can be hemmed. One 2 cm too short cannot be rescued.

Still not sure?

Write your numbers down and keep them — even if we come out and measure for you, it is a useful cross-check. Our team measures every opening on site before anything is cut, and the numbers you give on the booking form stay marked as approximate until then, exactly so nobody cuts fabric to a guess.