How much fabric do I need for curtains or roman blinds?

Terry Baskeyfield | Posted

Measuring a window correctly and working out the position of the fittings is a vital part of the preparation. Looking at your window try and imagine the window dressing finished! How will they look open and closed? Consider how high the window dressing will be above the window to achieve the appearance you're after. All of this will help with the next few steps.

Pattern repeat considerations

Note: Different fabrics on our site have different pattern repeats, so for someone new to making their own curtains or roman blinds working out all of the below can be a little daunting. That is why on the product page of our fabrics we have a size calculator that automatically takes into account the specific pattern repeat of the fabric you are looking at. So if this is your first sewing project we would highly recommend that you use the fabric calculator to ensure you order the right amount of fabric for your curtains or roman blinds.

Now, if you have chosen a plain fabric then you won't have to add any extra to your measurements, as there will be no need to match a pattern from one curtain panel to the other. However if you have a fabric with a pattern (pattern repeat larger than 1cm for example) then the pattern of the fabric needs to be taken into account and the overall amount of fabric required adjusted. This is because if you have a multi-coloured floral fabric with a pattern repeat of 30cm, then this means that the pattern will repeat (the same blue leaf, for example) will appear on the fabric every 30cm. This means that the bottom of each curtain will need to start at the same part of the pattern, so that all the blue leaves are at the same height on each curtain panel.

Therefore if you have a curtain panel that requires 100cm of fabric (finished length plus hems) then you might think you could just order 2 metres of fabric (100cm for each panel). However, with a pattern repeat of 30cm, where you want the pattern to sit at the same position on both curtains, you will find that a 100cm length of fabric will use 3 ⅓ pattern repeats (or 4 full pattern repeats, including the 20cm excess). Therefore when it comes to making the second curtain panel, if you have only ordered 2 metres of fabric then the fabric for the second curtain panel would be 20cm too short. So in this example you would have to order 2 ½ metres, not 2 metres to fulfil this order. However fabric is only sold in full metres on our site, so in this example you would have to purchase 3 meters.

The same considerations relating to pattern repeat also need to be taken into account when there is a join in your curtain or blind. If done correctly this will ensure that all parts of your curtain or blind are aligned properly and that you don't run out of fabric before completing your project.

How much fabric do I need to make curtains?

As mentioned above the pole or track fittings should ideally be in place before measuring for fabric, as they can be used as a guide for your measurements. This is because measuring window recess doesn't give you an accurate measurement for your curtains, as curtains sit outside of the recess. So really you need to measure the width of your pole or track. Here are our guides for measuring your window for a pole and track:

Once you have measured, you are now ready to calculate how much fabric you need. Most curtains require a minimum of double fullness depending on the heading and the look you want to achieve. We recommend using 2.5 times fullness to create a luxurious look.

  1. First, you will need to multiply the width of your rail by two.
  2. Divide this by the cut width of your fabric i.e 137cm/ 54”.
  3. Round up to the nearest full number, this is the amount of widths you need.
  4. Take the final drop measurement making allowances for any hems and pattern repeats (see above).
  5. Multiply this by the number of widths, this will give you how many metres you require. 
  6. Round this number up to the nearest whole number

Example with numbers:

  1. Track width 150cm, times by two equals 300cm.
  2. 300cm divided by a fabric width of 137cm is 2.18.
  3. 2.18 rounded up to the nearest number equals 3 widths.
  4. Finished drop is 225cm (allowing for hems and pattern repeat)
  5. 225cm multiplied by 3 fabric widths equals 6.75.
  6. 6.75 rounded up to the nearest number is 7, so 7 metres would be required.

How much fabric do I need to make a roman blind?

Again try visualising the window dressing and imagine the blind being open and closed. The important point to remember is that roman blinds require more space to stack at the top due to the blind folding rather than rolling. If fitting above the window recess this can make the window look longer. However if blind is to sit inside the recess you will lose some light because of the stack back.Roman blinds can be very economical as they often only require a few metres of fabric.

Firstly, decide on the final width of the blind, measure in several places to ensure you’ve considered tiles or other obstructions within the recess. Remember to keep an eye out for window handles, latches and cornicing as these can get in the way and may dictate where you will have to install the blind. For the length of the blind measure from the top position of the blind to just below the sill or to the sill if it’s inside the recess.

  1. Take your final width of the blind and add 10cm for side seams. If this measurement is larger than the fabric width then you would need to add a join to the fabric. See examples below for single width and joined blinds. 
  2. Take your final length measurement and add 15cm for the heading and hem. Always allow extra for pattern repeat too (see above).

Example with numbers (single width blind):

  1. The final width of the blind is 120cm, then add 10cm for side seams which equals 130cm wide (this fits within a width of 137cm fabric, so you wouldn't need a join).
  2. The final length of the blind is 160cm, then add 15cm for the heading and hem which equals 175cm drop. Rounded up to the nearest full metre equals 2 metres. So as you don't need a join, you will just need 2 metres of fabric to make this blind.

Example with numbers (joined roman blind):

  1. The final width of the blind is 160cm, then add 10cm for seams which equals 170cm wide (this doesn't fit within a width of 137cm fabric, so you would need a join).
  2. The final length of the blind is 160cm, then add 15cm for the heading and hem which equals 175cm drop. As you need a join (so will have two drops of fabric) you will need to times this number by 2, which equals 350cm. Rounded up to the nearest full metre equals 4 metres of fabric to make this blind

In Summary

The above methods outline the way to measure your fabric for curtains and roman blinds, as well as giving a detailed explanation of how to adjust your measurements for pattern repeat. If you struggle using this method then we would advise you to use our size calculator instead. This simple tool takes the pain out of working out how much fabric you need and does the hard work for you. It is available here (where pattern repeat and fabric width need to be entered manually), as well as on the product page of all of our fabrics (where pattern repeat and fabric width is automatically taken into account). Simply input a few measurements (such as width and drop) and voila the calculator tells you exactly how much material you need.

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