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Curtain Measuring Guide

Before you make or order curtains or drapes it is vital to measure your window dimensions accurately and decide the size of the curtains you want. Have you ever wondered how to measure for new curtains? Well we hope we can help you avoid expensive mistakes.

Measuring for and hanging curtains is straightforward in many situations and can be done by anyone competent in DIY (do-it-yourself). However, there are some situations where it is advisable to employ an expert. These include:

  • Bay windows
  • Slot windows; very narrow, tall windows, dormer windows
  • Windows without sufficient wall space above the window for a pole/track
  • Windows without plenty of wall space on either side
  • Non-rectangular windows (e.g. circular, triangular,)

But for most situations you will be using either a curtain track or pole across a flat rectangular window. So there are only two measurements of importance. When measuring use a sturdy metal tape measure, have a spirit level handy to check whether poles, batten, floors etc are truly level. Use proper safe steps if you are working at height and for large windows have an assistant hold the other end of the tape.

The old adage “measure twice and cut once” holds true!

How to measure curtain width

Start by measuring the width of the window horizontally across the recess occupied by the window & its frame. [Note the width of a window is not the width of the glazing.] Now add 20-30cm (8-12″), on each side since the track or pole should extend beyond each side of the window to enable the curtains to be drawn well back. A large window has more fabric in the curtain and so needs more space either side to pull back completely.

If there is insufficient space on either side of the window you may have to adjust your design and it would be better to get some expert assistance.

You may find a pre-existing wooden batten above the window and this should similarly extend beyond the window aperture. If it does not you may consider replacing or extending the batten. If you are fitting a track then the batten will be useful, whereas if you are fitting a pole the batten can be an awkward obstruction.

When you buy a pole make sure that the pole length (distance between finials) is equal to or greater than the required width and ensure that you can cut the pole length down to the desired size.

Where can I get designer fabric for my curtains? - Fabric Gallery & Interiors

How do I measure curtain drop?

Curtain drop is the distance between the top and bottom of the fabric in the finished curtain, and it depends on the style of curtain heading, positioning of the pole or track and the position of the bottom of the curtain. When installing a curtain pole aim to position it above the window so that the top of the curtain fabric is at least 10cm / 4inches above the top of the window recess.

  • Curtain Poles with rings: As a rule the top of the curtain should be just below the rings so measure the drop from the bottom of the ring.
  • Curtain pole with eyelet curtains: In this situation there are no curtain rings and the top of the curtain will be above the pole. Measure the drop from the top of the pole and add 4 cm to allow for the amount of curtain that will be above the pole.
  • Curtain poles with tab top curtains measure drop from the top of the pole.

For all curtains you need to decide where the bottom will finish:

  • Full length (A); the curtain finishes 1.5cm above the floor. This measurement needs precision because many floors and poles are not absolutely level. Measure the drop from an installed pole or track in three places, the centre and to the left & right. Work with the smallest measurement but double check that the track or pole is level. If in doubt check the slope of the floor.
  • Below sill length (B)); often curtains finish part way between the sill and a wall mounted radiator. Sometimes they hang over the radiator but this channels warm air up behind the curtain and so does not help keep the room warm. Decide where you want the fabric to end.
  • Inside window recess (C); the curtain finishes just above the sill. Sometime a very deep sill (often in a bay) necessitates this design.
  • Sill length (D): the curtain should finish 1cm above the sill (but note that this will let more light into the room).
  • Pooled; compared with full length curtains these usually have an extra 30cm /12 inches of fabric to pool onto the floor. These  can help if you have a seriously sloping floor in an older property.

How to measure for curtains; various positional options


Once you have width and drop give these figures to your curtain maker. They will be able to calculate the quantity of fabric you will need and the cost of making up the curtains. You will also need to agree on the curtain heading and on the type of lining for your curtains. And most importantly you’ll need to make your choice of curtain fabric.

Advice on choosing fabrics for curtains from Fabric Gallery & Interiors

All this may seem hard work but you will benefit from bespoke made-to-measure curtains that fit your window perfectly. And that’s something that ordinary curtains rarely can achieve.

If you do not know a good curtain fitter your first port of call should be your local curtain shop or interior design shop as they will be able to help. In the York area we can help.

If you found these tips helpful, we’d appreciate a “like” on our facebook page.

Disclaimer: this information is for guidance purposes only. We are not advising you to fit poles or curtains yourself. And we cannot accept any responsibility under any circumstances for the outcome if you choose to act upon this information. Our fitters normally only fit curtains that we have supplied because we will have also measured and made the curtains. If you need help fitting curtain poles here is some help.