Curtains: How to calculate the quantity of fabric you need.

Measure twice ... cut once!

If you’re looking for new curtains or sewing your own ones for the first time, you’d rather like to know or understand how much fabric you will need. Here are the different aspects you need to consider. Is the fabric plain or does it have a pattern? Does the fabric have a tendency to shrink? What is the width of the seams, the type of pleats and also the length of the curtain rod???… It can easily become overwhelming. 

The easiest way to explain it is by taking an example. Here are the characteristics of the fabric and the curtain rod:  

  • it’s a cotton fabric with a shrinkage of 6%
  • the width of the fabric is 140cm
  • the hem at the bottom of the curtain is 16cm wide and doubled
  • the seam allowance at the top of the curtain is 5cm 
  • the pattern-repeat in the height is 62cm  
  • the total length of the finished curtain is 2,85m (from the edge of the pleats at the top of the curtain to the edge of the seam at the bottom) 
  • the pleated tape with 1:2,2 (ratio of unpleated to pleated material required) 
  • the curtain rod is 1,80m long.
  • it is a classic decoration with 2 curtains (one on each side)

Here are the different points you’ll want to consider when you buy the fabric. 

1. Calculate the length of the fabric panel. 

a) You first want to calculate the panel just as if would be plain (without pattern). 

  • the wished final length:                                  285cm
  • the double hem at the bottom:                       32cm (16 x 2)
  • the seam allowance at the top:                         5cm
  • Total = 322cm

b) Consider the shrinkage value : 322cm + 6% = 342cm (rounded)

c) Considering the pattern repeat

  • the length you calculated above divided by the height of the pattern: 342cm / 62cm = 5,51….
  • round up to the next round value = 6
  • multiply the height of a pattern-repeat by this value: 62cm x 6 = 372cm

            The length of 1 panel is: 372cm or 3,72m long

2. Calculate the number of fabric-panels you need.

An easier way to create the pleats on your curtains is to use a pleat tape. This is also what a lot of professionals would use. It is easier and gives an accurate and consistent result. When using pleat tape you will usually get an indication of the ratio 1:2 or 1:2,5 for example. Our example uses a pleat tape with a ratio of 1:2,2.

a) The final width of the curtain (pleated curtains): 90cm (length of the rod divided by 2

b) The amount of fabric needed for the pleat tape: 90cm x 2,2 = 198cm

c) In addition, for the width you would add about a total of 10cm for the seam allowance on both sides of the curtain.

d) The quantity of fabric you need in the width is 208cm (198cm + 10cm).

How many panels in the width= 208cm / 140cm (the width of your fabric)

The quantity of fabric panels you need is 3. (1,5 for each side).

3. Total quantity of fabric you need is

The length of a panel 372cm x 3 = 1116 cm of fabric or 11,20 meters.

Well, if your head is spinning with all the calculations don’t hesitate to leave me your questions. Remember, measure (and calculate) twice… cut once, then enjoy your new curtains!

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