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How to Calculate Fabric For A Roman Blind

calculate fabric for a roman blind

Are you making a roman blind at home?

There’s a few things you’ll need to work out before you start, and as roman blind experts, we’re here to help! Once you’ve chosen your fabric you’ll need to calculate everything you need to complete the project, so lets get started!

Before you start

Before you start, you will also need to have your measurements, Check out our tutorial on how to measure for a roman blind to complete this step. This tutorial also includes choosing whether your roman blind will hang from a cassette or use a traditional fixing system.

If you’re not yet sure if a roman blind is right for you, take a look at our guide to choosing a fabric blind type, to explore your options.

How much fabric to make a roman blind?

To work out how much fabric you need to make a roman blind you’ll need to know a few key facts:

  • Your window measurements as above
  • The width of your fabric
  • The pattern repeat.

You’ll also need to decide what kind of lining you want to use. We sell a few lining options – take a look. You’ll also need to choose if you’re going to add interlining to your blind. If you’re not sure of the options, take a look at our post to help you choose the type of lining and any interlining.

Useful to know: Bear in mind that if you choose blackout lining for a roman blind there will be some small holes where the lines of stitching are completed, and some light will probably get in around the edges of blind also depending on how it is fixed. Fitting your blind outside of the window recess will help with this.

Now lets calculate the show fabric!


How many widths (drops) of fabric?

The width of fabric you need to make the blind is the finished width of your blind plus 10cm/4 inches for turnings.

If this is less than the width of your fabric then you only need 1 drop.

If it is more than the width of your fabric then you need 2 drops. We don’t recommend making blinds wider than this – it’s better to use multiple blinds to cover a very wide window.

If you are using 2 drops you’ll have to join widths of fabric. Usually we have a full width of the fabric in the middle with pieces on either side. You can even choose to use a plain contrast to the main panel.


How long is your blind?

The length of fabric needed for a blind is the drop of your blind plus 20cm/8 inches.

This means that if you are making one blind with one width of fabric then the amount of fabric you’ll need is the length of your blind + 20cm.

If there is a pattern on your fabric we would recommend adding half a pattern repeat so that you can choose the positioning of your blind on the fabric. For a plain fabric with 2 widths just multiply the length of fabric needed by 2.


What about the pattern repeat?

Are you using a patterned fabric? If you are joining widths of patterned fabric for a wider blind or have multiple blinds in the same room then you will need to consider the pattern repeat. We use a sum to work out how much you need to add for the pattern repeat; don’t worry, just work through the steps!

For this you’ll need to know what the pattern repeat of the fabric is. We always list this on our fabrics, or you can measure it yourself. Check out how to do it here:

Working out the show fabric with a pattern repeat:

You’ll need to divide the length of the fabric needed for each drop of your blind by the pattern repeat and round up to the next whole number. Here’s an example to show you how, working with a 64cm pattern repeat:

  • Your blind is 95cm long. Add on the 20cm (step 1) to give you 115cm.
  • Your pattern repeat is 64cm
  • Divide 115 by 64 = 1.79.
  • Round this number up to 2.
  • Multiply the pattern repeat by this rounded up number: 2 x 64cm = 128cm. This is the measurement for each drop.
  • Now multiply this by the total number of drops you’ll need for your blind or blinds: In this example we need 2 widths: 2 x 128cm = 256cm or 2.6 metres.
  • For fabric with a large pattern we recommend rounding this up a little to allow you more leeway to position the pattern on the blind. We’ve found we don’t like cutting off animals’ heads on our blinds!

Calculate the lining for a roman blind

You can make roman blinds using sew-on roman blind tape, or by making pockets within the lining to take the rods. The amount of lining fabric you will need depends on which way you decide to make your blind.


Calculating lining using roman blind tape

the lining calculation is the same as for plain fabric for the blind:

Blind drop plus 20cm/8 inches multiplied by the total number of widths of fabric for your project. This assumes the show fabric is standard width.

Note: if you are using extra wide fabric for your blind, calculate the number of widths of lining separately, as in step 1. Alternatively you could use extra wide polycotton lining.


Calculating lining using sewn pockets

If you are making pockets for your rods out of lining, you’ll need more fabric to do this, so add an extra 5cm of lining for every rod on every width of lining. As a general rule we recommend using 4 rods on blinds up to 1.4 metres (54 inches) long, and 6 rods on blinds up to 1.6 metres (62 inches) long. For more details check out our guide to calculating roman blind accessories.

Lets look at our example again:

  • Our 95cm blind would have 4 rods.
  • Length of blind + allowance: 95 + 20 = 115cm
  • 4 rods x 5cm per rod = 20cm
  • That gives us 135cm of lining per drop, multiplied by 2 drops giving a total of 2.7 metres.

Calculate Interlining for a roman blind

To calculate interlining needed, use the same calculation as for a plain fabric. You will not need to add pockets in the interlining, and it will be held in place by the lines of stitching for the rods.

Next Steps for your Roman Blind

You are now ready to move on and calculate the components and accessories you will need for your roman blind. All too daunting? Remember we can always make roman blinds to measure, and will take care of all the headaches of calculation. Just let us have your fabric choices and window measurements and we’ll do the rest.

You can’t currently order roman blinds on the website, but we’re always happy to give a quote or take your order by phone or by email!

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