Materials
  • - Fabric
  • - Lining
  • - Thread
  • - Heading Tape
  • - Weights
  • - Curtain Hooks
  • Tools
  • - Sewing Machine
  • - Needles
  • - Pins
  • - Clamps
  • - Scissors
  • - Set Square
  • - Straight Edge
  • - Invisible Marker
  • - Tape Measure
  • 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:

    * Note: Rounding down results in less full curtains, we aim for a fullness ratio of 2.5 but not any higher.

    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

    Emily

    Hello,

    When you add an extra pattern repeat to choose where the pattern starts, do you need to do this for every window you want to pattern match? E.g. say you want 4 matching pairs of curtains in a room, you work out the number of fabric widths and adjusted cut drop for each window then add 3 extra pattern repeats on top so that you can have each window matching?

    Thanks

    SewHelpful:

    IF the 4 pairs of curtains are exactly the same, ie same length and pattern repeat in the same position, you only need 1 extra pattern repeat. 

    IF the 4 pairs of curtains are different, ie different lengths, you will need an extra pattern repeat for each pair to position the pattern in the right place.

    Fiona

    If you are calculating how much fabric to buy online, how can you tell if your fabric has a half drop pattern repeat? The one I am considering has a 5.5cm horizontal and 5.5cm vertical pattern repeat.

    SewHelpful:

    The retailer should be able to tell you. Ask them. That size pattern repeat is unlikely to be a half drop.

    Helen

    Hi, how much heading tape do I need? I imagine it would be the same as the finish curtain width, which for me is 147cm (So I'd buy 3 meters of heading tape)

    SewHelpful:

    The info for this is in Step 8. You basically need a length the width of the pre pleated curtain panel plus 20cm for each curtain. Not the finished curtain width (that is the width after the tape is pulled and the pleats are formed)

    Charlotte

    Hello

    I have a fabric that has a 73.5cm pattern repeat.

    My window/door size is 420cm wide by 204cm drop

    My finished curtain length with be 232.5 and 8 widths in total.

    While calculating my adjusted cut drop the number is 3.16 if I round up to 4 the adjusted cut drop will be 294 if I am multiplying this by 8 it is going to a lot of wasted fabric in the end but can I get away with rounding down to 3 for my adjusted cut drop? I am getting a little confused as you can appreciate it is a large amount of fabric difference to waste if I rounded to 4. Look forward to hearing from you!

    SewHelpful:

    Large pattern repeats can cause a lot of wastage. We would try and get it down to 3 pattern repeats for the adjusted cut drops if possible rather than 4 to try and save 5.9m of fabric .

    The first thing to look at is the hem size. We would look to reduce it from a double 10cm (20cm fabric) hem to a double 8cm (16cm fabric) or a double 7cm (14cm fabric) hem. If you do this remember to reduce your lining hem by the same amount.

    In your case you say the  finished curtain length with be 232.5cm.  Don't you mean the finished curtain length is 207.5cm and the required fabric cut drop is 232.5cm?

    If that is the case 3 x your pattern repeat is 3x 73.5 = 220.5cm, that gives you 13cm for the heading allowance and hem allowance.

    With 13cm you could possibly get away with 3cm allowance on the heading rather than 5cm and a 5cm double hem rather than a 10cm double hem. Personally we would not go for this feeling it would too much reduce the quality of the finish of the curtain we were making, it is up to you.

    If you do decide to go ahead and make such a small hem, be aware that very often the actual pattern repeat of the fabric is not exactly the same as specified, we have had discrepancies of up to 4cm in the past. If your pattern repeat is any shorter than the 73.5cm it will cause you real problems!

    Jacky

    The fabric I have chosen is very heavy and thick, with a sort of patchwork so very irregular in texture (looks great tho!) Do you recommend double width for this? The window is 310 cm wide and with a drop of 230cm.

    SewHelpful:

    Despite the thickness of the fabric, on a pencil pleat curtain with a 310cm pole using the minimum fullness ratio of 2 we would not round down to 2 widths per curtain we would round up to 2.5 widths per curtain. 

    In our experience using less than double the fullness (fullness ratio of 2) makes the curtain look skimpy.

    Phyllis

    Can you be over generous on curtain width? I have a 2 metre track, however, as I was unsure of about cutting half or three quarter widths, I use 2 full widths for each curtain and each finished curtain is 2.6 metres wide. Would you suggest I reduce width of each curtain or, by pulling cords in heading tape tightly would I get away with leaving them at full widths? Thank you.

    SewHelpful:
    We think provided you are not using a very thick heavy fabric you should be ok. We would pull them to the required width and see what they look like.

    Sara

    I am getting a little confused about the heading allowance. Does it always stay at 5cm even if the heading tape is bigger (i.e. 7.5cm tape)?

    SewHelpful:

    You only need 5cm because the fabric is folded over at the top and the tape sits on top. The tape sits about 0.5cm down from the top and covers the cut edge of the fabric. With a bigger tape, 5cm heading allowance is still fine.

    Camilla

    I am making two sets of triple pleat curtains for 2 windows in the same room. Window 1 requires exactly 2 widths of fabric. Window 2 requires 2.5 widths, which I have rounded up to 3. My question is should I use all 3 widths (i.e. 1.5 widths per curtain) for Window 2, or cut it down to 2.5 widths (i.e. 1.25 widths per curtain) in order to maintain the same fullness ratio as Window 1? Is it very noticeable to have difference fullness ratios with triple pleat? Many thanks in advance.

    SewHelpful:

    We would make up the first curtain  then work out what width is required to make up the curtains for the second window to exactly the same pleat and gap size as the first window. We would then cut the 1.5 width panel down to the exact size needed when making the curtains for the second window.

    Terri

    Hi I'm a complete novice and am looking to make a pencil pleat curtain for a window fitting 1.9 x 3.1. The fabric I have chosen is expensive and I'd like to limit how many metres I buy. The fabric width is 1.36. Would it look completely ridiculous if I keep each curtain width to this number (1.36) rather than adding on an extra amount of fabric? I thought it would look OK as it's 3/4 of the width anyway but my mother seems to think otherwise! Help please :)

    SewHelpful:

    We agree with your mother they wouldn't look right. In our experience when you try and skimp on fabric with a pencil pleat heading you end up with skimpy curtains and that would not justify your expensive fabric and the effort used to make the curtains. 

    We we would always use the correct fullness ratio for a pencil pleat header.

    Fiona

    Thank you for this tutorial, it is very helpful. I have calculated my fabric which has a 64cm half drop pattern repeat. I have followed the instructions but am slightly confused about the difference between whole and half pattern repeat when calculating fabric. My understanding of the instructions is that I calculate the same as if it were a whole pattern repeat ie. the no. of widths (6) multiplied by ACD (192) add 1 pattern repeat (64cm)? When you say add 1 whole pattern repeat is this 64 in my case? Or do I double this as it is half pattern repeat? I would be very grateful if you could clarify or check my calculations (no. of widths 6 x ACD 192cm + 1/2 pattern rpt 64cm = 12.16metres of fabric?) Many thanks

    SewHelpful:

    In our experience when suppliers say a fabric is a (pattern repeat: 64cm half drop) that generally means the whole pattern repeat is 64cm and it is a half drop fabric. (so the half a pattern repeat is 32cm). If you are unsure, you need to measure on the fabric and be certain what the whole pattern repeat measurement is or if you don't have the fabric, clarify this measurement with the fabric company.

    Have you read the half drop pattern repeat tutorial on the website? There is an image that shows you what a whole pattern repeat is on a diagram and how the fabric drops down half a pattern repeat when joining it. The tutorial explains that you add one whole pattern repeat to your calculation and use half of this to position the fabric and the other half to compensate for the half drop pattern repeat when cutting the drops. 

    I'm afraid we don't make or check calculations (it would open the flood gates), but for a pair of curtains the key points when calculating, are your adjusted cut drop needs to be a number of whole pattern repeats and you add one whole pattern repeat to your total to allow for the positioning of the pattern and compensate for the half drop. .

    Lisa

    I wonder if you could advise me. I am making some window dressings and the FINISHED width of fully gathered curtains needs to be only 50cm. what is the maximum width of fabric I can gather into 50cm. I really wanted to keep it simple and go with a full width but wondering if this will be too much?

    SewHelpful:

    A full width (assuming 137cm)  will be just over 2.5 fullness ratio. We think you will be ok using that for your 50cm curtain.

    Rosy

    Could you advise me, I am going to make bay curtains with a 2 fullness ratio for a 4m bay pole, and I have rounded up to 6 widths. My fabric has a 32 cm pattern repeat, is 137cm wide and I make my adjusted cut drop 224cm (finished curtain length 180cm). Following your calculations I need 13.5m of fabric, but that does not seem enough - have I gone wrong?! I thought that I needed close to 16m (but that was without your wonderful and detailed notes) before I tried to replicate your calculations. Can you et me know if I am just doing this wrong!

    SewHelpful:

    You have gone for the absolute minimum fullness ratio effectively 2.05. If you want a thinner look that would be fine. However we would probably be looking to use 7 widths  (3.5 widths per curtain) for a slightly fuller curtain in a bay like you have described (fullness ratio of 2.39). That would require an extra adjusted cut drop and also don't forget to add an extra pattern repeat to position the pattern. 

    That comes very close to the 16m you were thinking of.

    Samantha

    Hi,my window track is 200cm, I want each drop of curtain to be 180cm (this already includes the top heading allowance and the bottom hem), the fabric is 140cm in width, I know I will need 3 drops of fabric but I don't know how to calculate how much fabric I will need because this is a patterned fabric with a vertical pattern repeat of 64cm. Please help!

    I am not sure whether this fabric has a whole pattern repeat or half drop repeat (I don't know what they are anyway) :(

    SewHelpful:

    I'm afraid we don't do calculations for people (there would be too many requests).

    If you have a normal pattern repeat you will need to work out the adjusted cut drop. Details of how to do that are above. You are basically rounding your cut drop up to the next whole pattern repeat, You do this because you have to cut each patterned drop as a whole number of pattern repeats to make sure each drop is cut in the same place in the pattern.

    To find out if you have a half drop pattern repeat or not, ask your retailer, otherwise watch the video above or read our "half drop pattern repeats explained" mini tutorial. That will explain what a half drop PR is and you will be able to see if you have one or not and how to deal with it.

    Ruth

    I am making curtains for a 9ft pole that i don't intend pulling closed. Would a width and a half each side look full enough for pencil pleat full length that will be tied back?

    SewHelpful:

    That would be the absolute minimum we would use. Interlining would make them look fuller.

    Denise

    I plan to make curtains that fall below a window sill, but will be above a radiator. What hem allowance should I use?

    SewHelpful:

    The curtains you describe are what we would call sill length not full length. So we would use the sill length hem sizes given in the instructions.

    Jenny

    How do you calculate how much fabric you require if you have a vertical and horizontal repeat in the curtain fabric?

    SewHelpful:

    All pattern fabrics have a vertical and horizontal repeat. You only need to worry about the horizontal repeat if you are doing something complicated like pleating to pattern repeat in a hand pleated curtain. Otherwise you calculate the horizontal amount in terms of widths of fabric and the vertical drops in terms of adjusted cut drops (each a whole number of vertical pattern repeats) as per these instructions.

    The only slight difference that can arisie, is if your fabric has a half drop vertical pattern repeat. There is explanation of what to do in this case on the website.

    Joanne

    Hi is there any reason why I should not turn the fabric and use the width I.e. 137cm fabric to make the the finished drop, meaning I would not need to join fabric widths. Thanks. Joanne

    SewHelpful:

    Yes we've done that before lots of times. Make sure you have enough for your heading and hem allowances and that you are happy with how the fabric will look orientated that way.

    Hayley

    Hi there

    I'm making a door curtain & im not sure if double the width of the track would work out too bulky.

    Anyone there used less & whats the end result

    SewHelpful:

    We would use double minimum, with pencil pleat we would probably use 2.5.

    Arabella

    Hello,

    I am making pencil pleat curtains with 1.5width in each using a standard pattern rpt. Each width matches in the middle as per your instructions but I am puzzled as to what happens when the side hems are then made and the curtains are drawn. They should overlap slightly but they will then not match? Please advise. Many thanks

    SewHelpful:

    Yes they will not match exactly as you say due to overlap and the extra fabric that may be needed in the side turn -  but will be close, and will be inline horizontally,

    You can match at the join but it is beyond the scope of this tutorial.  It is also very dependent on what the pattern of the fabric is like as to how much fabric you will lose and extra you may potentially need to buy.

    If you really want to get a perfect match at a point in the overlap you can do it by finding the right points in the fabric panel to fold over the leading edges of the curtain panels. This will lead to a loss of fabric, lose fullness of the curtain and with a fabric with a large horizontal pattern repeat a loss of a lot of fabric that may make the curtain panel width unviable so you would actually have to sew more fabric on the on the far sides of the curtain panel to get enough width. You also need to get both fabric panels the same size so the join comes in the middle of the window.

    You need to measure your horizontal pattern repeat and work out how much fabric you are going to lose, you will probably find with a large horizontal pattern repeat you are probably best to make each fabric panel half a width more wide than required,  trim them down so the leading edges turn at the right place and then trim the outer sides so you get the correct width for each panel. 

    These are calculations you need to do before making as it can affect how much fabric you need to buy, especially with a large horizontal pattern repeat. 

    Due to all the extra work involved and potential extra fabric that may need to be purchased it is not something that is generally done.

    Sarah

    Please can you advise why you need a hem allowance of 20cm for full length curtains. This seems excessive to me and when I measure the hem of other curtains they are generally 5 - 7cm. Am I missing something / not understanding this correctly?

    SewHelpful:

    We use a hem allowance of 16cm for a sill length curtain and 20cm for a full length curtain. The hems are folded double so the actual hems on the curtains will be 8cm and 10cm respectively.  We use 8cm hem on a sill length curtain and a 10cm hem on a full length curtain because we think they  look in proportion and right, plus the extra weight helps them hang nicely. However there are no hard and fast rules, you can use what ever hem size you like.If you are running into to trouble and need to save a little bit of fabric you can always reduce the hem sizes or have less of a fold.

    Petra

    Hi, I've worked out from your calculations that I'd need 2.2 widths of fabric for a 1.5m curtain pole. You suggest rounding up or down to the nearest number which would be 2 widths (one for each curtain, they're 135cm wide) ... Do you think the curtains would be too thin or is it just a matter of personal choice? Thank you, Petra

    SewHelpful:

    To get that figure you used a fullness ratio of 2.0. Which is lower than we would use for a standard pencil pleat curtain. We would definitely round up. If you round down your fullness ratio will be less than 2.0 which won't be enough.

    Sarah

    I find your tutorials invaluable. I have a question regarding fabric drop and fabric calculation. On a patterned fabric I understand the pattern drop needs to be taken into account as it affects the length of the fabric required, but what about the pattern width? When attaching two drops of fabric, the pattern needs to be matched down the seam widthways. How do you calculate for this (bearing in mind pattern widths are not usually given) and avoid it affecting the fullness of the curtain? Hope I have explained this correctly.

    SewHelpful:

    Standard patterned fabrics should join near the selvedges. so you generally only lose a few centimetres on the join. Most fabric companies give you the useable width. Typical figures are a flat width of 147cm and a useable width of 137cm.

    Diane

    I only need 2 widths of fabric for my pair of curtains, so one width per curtain - I am coming up with an ACD of 192cm and 3 pattern repeats, when I add a pattern repeat I need 448cm fabric for a track length of only 122cm. This seems an awful lot - do I need to add that fourth pattern repeat if I am only needing one width per curtain - won't the third repeat allow me to match the two curtains when they close, or is that 4th one necessary after all? Thanks for any help - this website if brilliant!

    SewHelpful:

    he one extra pattern repeat you add to the total is to enable you to position the pattern on the curtain. (It is not to position the pattern so they match in the middle -  the ACD ensures that) If you don't want to position the pattern you don't have to add the extra pattern repeat.

    Your pattern repeat is quite large, make sure you don't have a half drop pattern repeat. If you do have a half drop pattern repeat read our extra info and you will need the extra pattern repeat in the fabric quantity.

    Lizzie

    I am new to curtain making. I have just done the calculation for my pencil pleat curtains and, using whole numbers, the fullness ratio is coming out at either 1.8 or 2.8. Will either of these work? your guidelines suggest it should be at least 2.25 for pencil pleat curtains, but that over 2.5 is too high.

    Length of pole is 142 cm.

    SewHelpful:

    1.8 would be too skimpy.

    if you are getting 1.8 and 2.8 Fullness ratio with a 142cm pole length, that would imply your fabric is 128cm wide.

    If this is the case we would look to make the curtains with a 2.5 fullness ratio. To do that

    2.5  x 142  = 355cm

    ÷ 2    = 177.5cm fabric per curtain

    ÷ 128 = 1.39 widths per curtain

    Therefore we would use 3 widths to make the pair of curtains, but rather than make each curtain 1.5 widths wide, we would make them 1.39 widths wide. So we would trim the half widths down from 64cm wide to 50cm wide and then join them.

    Helen

    Hi, could you please advise what is the stack ratio for a single pinch curtain. I want the curtain to stack back completely off the Doors & Windows. Thanks

    SewHelpful:

    The stack back will depend on the thickness of the curtains and the size of your spaces between hooks ( the number of folds for a given width). Pencil pleat heading doesn’t stack as neatly at the top as a hand pleated heading.

    A couple of examples of curtains we've made

     1. 130cm wide lined hand pleated curtain stacks back to 35cm width

     2. 130cm wide interlined (medium weight) hand pleated curtain stacks back to 40cm width

    Tracy Hall

    I am making 2 single curtains for 2 bifolding doors with the same measurements.

    According to my calculations (and the online one) it would be better to have 4.5 widths of fabric and lining for each curtain to get the desired fullness.

    I have 2 questions.

    If I divide a fifth fabric width in half can I use each half for the 2 curtains?

    Where should I join the half panels on the fabric?

    Thank you

    SewHelpful:

    We put the half widths on the outside edge of a curtain. (not the leading edge you pull). You can split the drop for the half width in each curtain. But as you are making 2 single curtains on 2 different doors, are your curtains both going to be identical and pull in the same direction? or be like a pair pulling in different directions eg towards each other.

    If they are going to be identical and pull in the same direction then you will find you can only have the half width on the outside edge of one of the curtains (because you join selvedge to selvedge). It would be a waste of fabric and expensive to buy another drop to cut another half width though. So we would probably advise the customer to  just accept the half width on the leading edge of the second curtain to save money.

    Belinda

    I have read two different methods for calculating the allowance for pattern repeat. One said to add a pattern repeat to each cut drop, the other is to round up the number of the pattern repeats needed for each cut drop. They give quite different results, I see you use the latter and I'm curious as to which is the most reliable.

    SewHelpful:

    They both work, the first method means you will buy more fabric than is necessary and have more wastage.

    Jennie

    I have a 125cm rail and light to med wight material for some pencil pleat curtains. One width gives 2.1 fullness. Will this be enough or do I add a extra half width on each curtain or do I then cut some off as it will be nearer 3 x fullness. If I need to cut some off how do I work out how much to cut

    SewHelpful:

    1. That wouldn't be enough fullness for us using one width. 

    2. Yes and extra and cut it down to 2.5 fullness.

    3. half pole length x 2.5 = width of fabric panel (each curtain)

    Kate

    I have a fabric with a vertical stripe (I am new to this!) so I will need to apply adjusted fabric drop??

    Thanks!

    SewHelpful:

    No

    We are using the vertical pattern repeat here to calculate an adjusted cut drop. A vertical stripe will have 0cm vertical pattern repeat, but it will have a horizontal pattern repeat (distance across the fabric that the pattern repeats itself) which you do not need to worry about. (the fabric should join ok across the widths)

    As there is no vertical pattern repeat you will be able to treat the fabric as a plain fabric when calculating the qty.

    Sally Mallet

    I have a curtain pole of 137 with 142 drop, I have been sold 4.90 of material. The width of the material is 1.37 cm. Is this too much material? would a width and half be too full? I measured the whole length of the pole when giving my measurements to the shop, or would one width in each curtain be sufficient?

    SewHelpful:

    They have given you enough for 1.5 widths per curtain in plain fabric which is exactly what we would have went for. We have learnt it is a false economy trying to skimp on the fabric as the curtains look no where near as good, 4.9m is what we would have ordered.

    Jp007

    When joining the widths, do you add seam allowance? If so, how many centimetres seam allowance across the width for each seam

    SewHelpful:

    How to join fabric panels with a plain seam is shown in STEP 6 of the tutorial.

    With pencil pleat curtains you are making curtain panels up then pulling along the heading tape to reduce the panel to the required width. The fabric used in the seam when joining is inconsequential in comparison to the widths of the 2 fabric panels joined (about 270cm). Therefore we do not need to make an allowance for it in the calculations, it is effectively included in the fullness ratio.

    Julie

    Is it necessary to launder the fabric before making the curtains?

    SewHelpful:

    Different fabrics behave in different ways. Washing your fabric is fraught with the danger of it shrinking, fading and changing its feel.

    With the fabrics we use we never wash them and would not expect the curtain or blind to be washed after it is made. The only thing we do is press the fabric and lining before measuring and cutting. That way you avoid the curtain or blind shrinking later when you press it. Always take care when pressing the fabric and test a small piece first.

    Julie

    Is it necessary to shrink curtain fabric by laundering prior to making up.

    SewHelpful:

    We never wash fabric as we have had too many costly mistakes in the past with it fading, shrinking etc. 

    If you are making a curtain that needs to be washed and are confident your fabric and lining is washable, we would wash and press the fabric before making the curtains to reduce the chance of them shrinking when they are washed. It may be worth cutting a test sample of the lining and fabric to wash and press first.

    Sophie Bennington

    Hello, is 3x fullness too much for interlined pencil pleat curtains? For the window I am dealing with, 1 width per curtain gives only 2x fullness but 1.5 widths gives 3x fullness (too full?). Should I make up the curtains with1.5 widths or cut down the 1.5am widths to give 2.5 x fullness? Do I cut this excess from the half width?

    SewHelpful:

    Sounds like you have a short pole.

    We would use the 1.5 widths and cut them down to give 2.5 fullness. for us 3.0 fullness would be too much.

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