Materials
  • - Fabric
  • - Lining
  • - Thread
  • - Buckram
  • - Weights
  • - Curtain Hooks
  • Tools
  • - Sewing Machine
  • - Needles
  • - Pins
  • - Clamps
  • - Scissors
  • - Set Square
  • - Straight Edge
  • - Invisible Marker
  • Step 3: Calculate Fabric Quantity
    Printable Worksheet
    Printable Worksheet

    Fabric is ordered in a length of metres cut from the roll. Before calculating fabric quantities you will need the following:

    With this information we :

    • Calculate the NUMBER OF WIDTHS OF FABRIC required to make the pair of curtains
    • Calculate the FABRIC CUT DROP
    • Then Calculate* the amount of FABRIC REQUIRED.

    * Note: The final calculation depends on whether the fabric is PLAIN or has a PATTERN.

    NUMBER OF FABRIC WIDTHS

    To calculate the number of fabric widths required to make your curtains:

    • Multiply Pole Length by Fullness Ratio.
    • Divide this figure by the Fabric Width.
    • Round the result up or down to the nearest whole number*.
    • This whole number is the number of widths you require to make your curtains.
    * Note: When rounding up or down you are slightly increasing/decreasing the fullness of your curtains. Rounding down results in less full curtains and if using a fullness ratio of 1.9 the curtains can be too thin if you round down.

    FABRIC CUT DROP

    To calculate the Fabric Cut Drop

    * We also add a 5cm trimming allowance for PLAIN FABRIC to enable us to straighten the ends of the cut lengths, we dont for PATTERN FABRIC as there is usually extra fabric in the ADJUSTED CUT DROP.

    PLAIN and PATTERNED FABRIC are treated differently at this stage

    FABRIC QUANTITY REQUIRED (Plain Fabric)

    To calculate the amount of plain fabric required to make a pair of curtains:

    • Multiply the "Number of fabric widths" by Fabric Cut Drop.

    Alternatively try our online calculator.

    FABRIC QUANTITY REQUIRED (Patterned Fabric)

    This tutorial is based on a normal pattern repeat fabric, if your fabric has a half drop pattern repeat please read HERE and adjust the instructions accordingly.

    When the fabric has a pattern we also have to take into account that the pattern will need to line up where we join fabric and the pattern will need to be in the same position on each curtain.

    To enable this we adjust the fabric cut drop so we can get a cut drop starting at the same pattern position each time.

    ADJUSTED CUT DROP

    To calculate the Adjusted Cut Drop:

    • Divide the Fabric Cut Drop by the vertical Pattern Repeat
    • Round the result up to the nearest whole number
    • Multiply the whole number by the vertical Pattern Repeat
    • You now have the Adjusted Cut Drop (ACD)
    • The Adjusted Cut Drop is also a whole number of vertical pattern repeats, note this number down for use in measuring cut drops in step 6.

    FABRIC QTY

    To calculate the amount of patterned fabric required to make a pair of curtains:

    • Multiply the "Number of fabric widths" by Adjusted Cut Drop.
    • Add one vertical pattern repeat (this allows you to choose where the pattern starts)

    Alternatively try our online calculator.

    This video explains
    • The difference between half drop pattern repeat and normal pattern repeat
    • Adjusted cut drop

    Your Questions & Comments

    Angela

    This is my first attempt at making double pinch pleats. Do I subtract the length of the pole from the width of the curtain to work out the spacing for the pinch pleats

    Than you for your assitance

    SewHelpful:

    No. 

    We show you how to calculate pleat sizes and spaces in STEP 9.

    Rachel

    Hi - I've just made some edged Roman Blinds using your great tutorial and now starting to make matching patterned Curtains trimmed with a plain fabric 20cm wide leading edge but am having trouble working out how much fabric I need (i.e. how many fabric widths) to account for the additional edging. I haven't decided whether to make double or triple pleats but am working on a fullness of 2.25 and will adjust fullness (and therefore pleats) to be most efficient with fabric

    Pole length: 220cm

    Finished Curtain width: 118cm

    Fullness Ratio: 2.25cm

    Fabric width: 137cm (both plain and patterned)

    Using your calculator, it suggests I would need 3.6 widths (rounded up to 4) but this doesn't account for the edging.

    Is there any easy way to work out what I need or do I have to do it long-hand? If so, am I right to assume that the required fabric width is the finished curtain width X Fullness ratio plus any seam allowances?? (118 x 2.25 = 265.5 plus allowances approx 25)

    Using this assumption, I think that I will probably need 1.8 widths of pattern for each curtain PLUS the plain edging. If I am right, should I add the narrow edge to 1 x full width plus 0.8 width OR 2 x 0.9 widths? Which would look best? If 1 + 0.8 is advised, which should be the central panel?

    Grateful for your advice - thank you

    SewHelpful:

    We would use a minimum fullness ratio of 2.5 for triple pleats, If you are using 2.25 we would make double pleats working on approx 6 pleats per width.

    I'm afraid you have to do the calculations long hand and work it all  out. The seam allowances are included within the fullness ratio. The only thing you may need to add to the pole length are returns if you are having them on your curtains.

    Rather than specify a trim leading edge width at the start we would actually work out our pleats and spacing first, then calculate the width of the trim so it finishes at the right place on the curtain. ie at the first pleat, halfway through the first pleat, at the end of the first pleat etc.. rather than at a random place on the curtain.

    We would join the trim to the patterned fabric (note the trim fabric will have to include fabric for the join seam with the pattern, side turn and the depth of trim). We would then cut the panel down to the width we required taking excess fabric from the other side not the trim side. Of course your extra trim fabric could be making your panel up to the panel width you want so you may not need to cut it down.

    Rachel

    Hi I'm making with a fullness of 1.9, I've come up with fabric widths required of 4.456! Do you think I can get away with just 4 widths? I don't want the curtains to be too full or too 'bunched up' when open. Do you think I can get away with 4 widths? Pole length of 326cm!

    Thanks

    SewHelpful:

    It would be minimal, We would make up a dummy header and see what it is like before proceeding.

    Diana

    Hi

    I am making small double pleat curtains for a boat. Measurements are W45cm L 60cm. do I really need a hem allowance of 16cm? Also should I still use 1.9 ratio?

    SewHelpful:

    No the 16cm is just what we use for sill length curtains in a house. You can make the hem any size you like.

    We would probably go for less than 1.9 for that curtain. Initially thinking of using 5-6cm pleats with 10-9cm gaps. We would make a quick mock up and see if that looks right. 

    Jill Sharp

    Hi I am making interlined double pinch pleat curtains, I am using 3 widths in each curtain can you tell me where the seams should sit, should they sit inside the pleat or on the flat area between a pleat and also how much spring back should I allow per curtain. Also will the flat area on the inside edges be enough to cover the middle bracket on the pole so not to leave agap in middle when curtains are closed

    SewHelpful:

    We tend to have the seam in a gap rather than the pleat to avoid bulk in the pleat.

    in STEP 2 when calculating the finished curtain width we add 8cm to each curtain for ease and overlap.

    We don't know how big your bracket in the middle is, so you will need to work out what size leading edges you need (to cover this area where there will be no rings) in STEP 9 when working out your pleats.

    Lynn Nunn

    How much fullness do I need for a hand sewn french pleat valance with a finished width of 145cm plus 15cm x 2 for the returns?

    SewHelpful:
    If we are unsure if the usual fullness ratio is going to work with larger returns etc, we calculate slightly differently. We make a sample pleat the size we want it and see how much fabric that pleat requires. We then work out the  number of pleats+spaces and space sizes we are going to use. From that info (including your return sizes) we know what width panel we need to make, to pleat up.

    Terry

    Hi sorry this is going to sound a very basic question. Just trying to work out if we have enough material for double pleat curtains and it states a fullness ratio of 1.9-2.2.... what does this even mean? is it you're stating i need to add an additional 1.9-2.2 for each curtain on top of each curtain measurement. Or an additional 1.9-2.2 on the whole window size, or some other thing that I'm just not getting..sorry just a bit confused(I'm a man lol) as to what i'm adding 1.9-2.2 to. Basically I have been given a pair of very expensive, fantastic triple pleated silk curtains, which are huge and i'm trying to work out if there is enough material in them to make curtain for my 4 windows with the material. Thank you

    SewHelpful:

    When you make a curtain you effectively make a flat panel then you pleat it up , that panel becomes narrower at the heading where the pleats have pulled it together. If you were making a curtain that was to be 1m wide when it was pleated with a fullness ratio of 2.2 You would need a panel 2.2m wide before you pleated it up to make it 1m wide.

    Emma

    Hi there.

    My first attempt and double pleats and I forgot to allow for the buck rum depth in my calculation of fabric cut drop. Lengths are cut unfortunately for the first curtain and I don’t have enough excess in the middle panel. Could I hem the top and add the buckram over it and pleat?

    SewHelpful:

    You can sew a strip of lining to the top of the fabric to fold over the buckram.

    Mary

    Does the 20 cm hem allowance for full length curtains include the bottom hem and the side hems? Also, do we account for seams of sewing the widths together? Thank you...

    SewHelpful:

    No and No

    The unusable selvedge edge of the fabric usually accounts for most of the seam allowance when joining.

    Kathryn

    hello,

    I am making large curtains ( 3 widths in each curtain)with a appx. 2.5 metre drop. My working bench is reasonable size but not as big as each curtain!!! Can you give any advice on how to handle such large quantities of fabric and still get good results?

    SewHelpful:

    It will be hard work, keep it all as flat and smooth as you can when working on it, Clamps are very good for holding sections in place on the table, if you haven't got clamps you can use weights. Spring clamps are pretty cheap on ebay though (make sure you don't buy tiny ones though)

    Lucie Rees

    I have a question about the required widths of fabric. Is the amount required for each panel or is it the amount required for the window if making two panels? I am making two panels for my window and based on calculations, I need 2 widths of fabric. I am unsure if that is for each panel or if each panel requires 1 width. Thanks!

    SewHelpful:

    The number of widths calculated is what is required to make both curtains if you are making a pair to cover the window, or a large single curtain if you are not making a pair.

    For simplicity the tuorial and it's examples are based on making a pair of curtains to cover the window.

    Bridget

    My fabric has a large floral pattern with a horizontal repeat of 30 cm positioned centrally on the fabric. There will be a lot of waste when joining cut lengths to make sure the pattern actually matches along the seams. Do I calculate number of widths required based on the actual width of the fabric (150 cm) or the width between the centres of the pattern closest to the fabric edges (120 cm)?

    SewHelpful:

    Your width measurement for the calculations is the usable width (what it will be when joined). A standard width is approx 137cm, sometimes a standard pattern gets printed on wider fabric that leads to wastage when joining, also have you check if  it is a half drop pattern repeat?

    Claire

    I am making a single panel curtain. Using your calculations, 3 widths seems not to be enough, but using 4 widths might be too full. The drapery material is a solid color. Is it ever okay to use a portion of a width of fabric?

    SewHelpful:

    Yes of course you can cut down to your required fullness.

    Fiona

    If each curtain will be one width of fabric, i.e. I don't have to join any panels, I assume I don't need to calculate adjusted cut drop. Do I just add one pattern repeat do the curtains will match?

    SewHelpful:

    We add one pattern repeat  to place the position of the pattern on the curtain.  Adjusted Cut Drops are then needed for the curtains to match. 

    "vertical pattern to be in the same position on each curtain"

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