Calculating the amount of
Curtain Material

Sometimes curtain material can be suitable for smaller windows or the material width is already half the width of the track.

The fabric can already be wide enough. The typical width of material is in a range from 45 - 60 ins (114.5 - 150cms) so this would mean that no joining will be needed.

Curtains for larger windows and especially bay windows would need the fabric widths sewn together.

In plain fabrics this is sometimes seen but the seam can fall into the fold so wouldn't be duly noticed.

If you were using patterned fabric you would need to buy extra fabric and join the patterns up first, otherwise if the pattern is large there would be one pattern on one side that didn't match up with the same pattern on the other side. 

This is referred to as the pattern drop.

The type of track or pole used can determine the fullness of the curtain. Many of the heading tapes, such as pencil pleat  look better if double width is used. This can be adjusted, if not as much gathering is wanted, to one and a half widths.

Eyelet and Tap top curtains use less material and usually require one and a half widths. The spacing between the loops or eyelet holes lets the fabric fold naturally.

Working how much curtain material is needed.

There is an imaginary window for the calculation example.

The window is 40 ins (100 cm) wide and 40 ins (100 cm) high. The curtain track extends 4 ins (10.5 cm) either side of the window. A plain material was used with a width of 48ins (120 cm) and the heading is a pencil pleat. The length wanted or finished length is 48ins (122 cm).

This window would have been measured first to get the finished length and the finished width.

Working out the fabric widths

In this example the width of the fabric should be twice the width of the track. 40+4+4=48 ins ( window width + extra track (left) + extra track (right) = track width) or 102 + 10 + 10 = 122 cm.

Multiply the width by the amount of gathering you want in this case it was multiplied by 2 = 96 ins (240 cm).

Then divide this by the width of the fabric in this case 48 ins (120 cm) = 2 widths. This is the amount per curtain. A pair of curtains would need 4 widths. The pleating would be quite tight.

Track width x gathering divided by fabric width = widths per curtain. X 2 per curtain pair.

Working out the fabric length

Now that the number of widths have been calculated the next step is working out how many yards or metres to buy. Measuring the length wanted or finished length (track to hem) then adding in the heading and hem will give the Cut Length.

In the example the length wanted is 48 ins (120 cm). The amount of fabric for one drop would be 48+6+2 ins = 56 ins (finished length or length wanted + amount for heading + amount for hem  or 120+15+5 = 140 cm. The cut length is 56ins or 140 cm.

Multiply the cut length by the total number of fabric widths. In this case  56 ins (140 cm) x 4 = 224 ins (560 cm) which is 6 + 1/4 yards or 5.6 metres. This can be rounded up to the nearest width so it would be 7 yards or 6 metres.

Length wanted or finished length + heading + hem = Cut length divided by number of fabric widths needed = Amount of fabric in yards or metres.

Eyelet curtain can need a double heading and for tab top curtains the amount of material for the tabs will need to be taken into account as well.

This reads more complicated than actually doing the making but you need to get the amount of fabric right or else you will only be making one. Which I have done in the past.

Now that the window has been measured and the amount of material has been calculated the next step is to sew the curtains.

Enjoy searching for your curtain material.

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