Calculate your curtain fabric
Are you ready to make some curtains? Here’s how to do a curtain fabric calculation!
Once you have measured your windows and chosen your fabric, you’ll have all the information you need to work out what you need to make your curtains, as well as the measurements for each cut. Don’t forget, if we are making your curtains, we only need your window measurements, and we’ll do the rest!
Here’s what to do:
This how-to guides you how to use a curtain fabric calculator to work out exactly how much curtain fabric, curtain lining and curtain header tape you’ll need to make your curtains. If you need more help, you’ll find all of our curtain making information gathered together here. If you’re not sure which curtaining lining to choose, take a look here. To calculate how much curtain fabric to buy, you will need to know the width of your fabric and, for a patterned fabric, the pattern repeat. These can be found on all of our curtain fabrics. It’s important to follow all the steps correctly, so take your time and follow the how-to carefully. Make sure you use the same units of measurement (inches or centimetres) throughout!
The instructions below will help you to calculate how much show fabric, lining and header tape you’ll need to make your own pencil pleat curtains, as these are the curtains most people make at home.
For our curtain fabric calculation, the width of our pole or track is 238cm, and the finished drop is 165cm. We’re working with a fabric with a width of 138 cm and a pattern repeat of 7cm. Don’t forget to use your own measurements throughout!
First decide how full (or gathered) you want your curtains to be. For double fullness, multiply the width of the pole or track by 2, like this:
Measured width 238cm
x 2 for fullness = 476cm
For less fullness multiply by 1.5. If you have more than one window in the room, you may need to make adjustments to match the fullness. Find out more about working with curtain fullness here.
Calculate the number of drops
Divide the number from step 1 by the width of your fabric:
476 / 138 = 3.44
Round this number to the nearest exact number. In our example we’ll round 3.44 up to 4. A total of 4 widths of fabric (drops) means 2 widths in each curtain.
If in doubt always round up, as fuller curtains look better.
How much fabric per curtain?
The easy bit! You will just need your measurement for the finished drop. In our example, this is 165cm.
Now we’re going to add a hem allowance to the drop. We usually add a hem allowance of 20cm (8″). This gives 5cm (2″) of turning at the top and a double thickness hem of 7.5cm (3″) at the bottom.
165cm + 20cm =185cm
Is there a pattern repeat?
Look for an obvious detail in the pattern, and check the fabric until you see the same detail again; now measure from one to the other. In our example the pattern repeat is 7cm.
Divide the total from step 3 by the pattern repeat, then round up to the next whole pattern repeat. Here’s our example:
185 / 7 = 26.42
Round up this number = 27
How much fabric for each drop?
Now multiply the whole number of pattern repeats from step 4 by the pattern repeat. This will give you the length of fabric you will need to cut for each drop of fabric:
27 x 7cm = 189cm
We will cut 4 drops of fabric each measuring 189cm. If your fabric pattern is a half drop repeat you may need more fabric to match the pattern widthways.
How much fabric do I need to buy?
Multiply the length of each drop (from step 5) by the number of widths you need (step 2) to get the total amount of fabric you need. In our example this would be:
189cm x 4 = 756cm or 7.6 metres of fabric.
Be sure to add in any extra fabric you may need for tabs, tie-backs, cushions, piping or pelmets.
How much curtain lining do I need?
To work out how much curtain lining you’ll need to buy, take the number of widths (from step 2 of the curtain fabric calculator) and the drop plus 20cm (step 3).
To work out how many metres of lining you’ll need for your curtain fabric calculation, just multiply the drop measurement +20 x no of widths:
185cm x 4 = 740cm or 7.4 metre of lining.
How much header tape do I need?
The last part of your curtain fabric calculation is for header tape. For pencil pleat curtains, different widths of header tape give quite a different finish. you’ll find both the standard 3″ header tape and our deep 6″ header tape on our web shop.
To work out how much header tape to buy, simply multiply the width of your fabric and the number of widths (step 2). Here’s our example:
138 x 4 = 552cm or 5.6 metres of header tape.
If you’re local to one of our shops, we’re always happy to help you with your fabric calculations! Just bring in the measurements of your window and fittings.