Half Drop Pattern
      Repeat Fabric
      CALCULATOR

INPUT

RESULTS

          Cutting Diagram


  1. Use up to 1/2 PR to position the top of the first drop.
  2. Cut the Adjusted cut drops marking them alternately A then B. They will all be the same length unless you are making a pair of curtains with an odd number of drops, in which case cut the last drop (which will be an "A") half a PR longer. You will have included an extra half PR in your fabric qty calculation for this purpose.
  3. Join the drops as in the "Joining Diagram"


  1. Use 1/2 PR to position the top of the first drop
  2. Number the drops
  3. Mark and cut the ODD drops (all the length of the ACD, except the last ODD drop is 1/2 PR longer).
  4. Then cut all the EVEN drops (again all the length of the ACD. Note: these ACDs will all start 1/2 a PR down on the pattern when compared to the ODD drops).
  5. Join the drops as in the "Joining Diagram"

          Joining Diagram



2 important points:

  1. The Calculator includes half a pattern repeat (PR) for positioning the pattern on your drops.(you may want to add an extra half PR to the total to give you a whole PR to position the pattern)
  2. The calculator calulates both length and number of pattern repeats for the drops. When cutting the drops measure in pattern repeats it is important you cut the fabric at the correct position on the pattern.

This method rounds the fabric cut drop up to a whole number of pattern repeats so is the best method when the cut drop is at least half way into the last pattern repeat.

  1. Calculate an Adjusted Cut Drop (ACD) using whole Pattern Repeats (PRs), rounding the cut drop up to the next whole PR.
  2. Multiply the ACD by the number of drops and add one whole PR to calculate the total fabric frequired.
  3. Use 1/2 PR to position the top of the first drop
  4. Number the drops
  5. Mark and cut the ODD drops all the length of the ACD, except cut the last ODD drop 1/2 PR longer.
  6. Then cut all the EVEN drops the length of the ACD. (Note these ACDs will all start 1/2 a PR down on the pattern when compared to the ODD drops.)
  7. Join the drops as in the "Joining Diagram"

More detail on this method >>

This method rounds the fabric cut drop up to the nearest half pattern repeat so is the best method when the cut drop is up to half way into the last pattern repeat.

  1. Calculate the Adjusted Cut Drop (ACD) in whole pattern repeats (PRs), but round the fabric cut drop up to the next HALF PR.
  2. Multiply the ACD by the number of drops and add half* a PR to calculate the total fabric required. Note:* Add a whole PR if you are making a pair of curtains with an odd number of drops.
  3. Use up to 1/2 PR to position the top of the first drop.
  4. Cut the Adjusted cut drops marking them alternately A then B. They will all be the same length unless you are making a pair of curtains with an odd number of drops, in which case cut the last drop (which will be an "A") half a PR longer. You will have included an extra half PR in your fabric qty calculation for this purpose.
  5. Join the drops as in the "Joining Diagram"

More detail on this method >>

Questions & Comments

Helen

Hi there, I am looking at the lewis and wood adams eden for 2 blinds and 1 curtain on the same wall which has a half drop repeat of 108.5cm. The blinds are one each side of the curtain (lhs and rhs). The curtain is 4 widths with a cut drop of 253cm so i have used the calculator to estimate 11.4m. I want to check if i have curtains running ABAB then if i want the blinds to run B on the left and A on the right how do i work out how much fabric i will need and get the pattern to all start at the same place if the blinds are going to be fitted at the same height as the curtains? The blind cut drop is 156cm. many thanks for your help!

SewHelpful:  

Hi Helen


I am so sorry but we are unable to make or approve calculations due to the large amount of comments we receive.


Kind regards


Cindy

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Jean Grainger

Am I using the vertical pattern repeat or horizontal pattern repeat from the fabric specifications?

SewHelpful:  

Vertical, there is an explanation of half drop pattern repeats HERE

Caz Hill

Hi Cindy,

I’ve made an error and joined odd 3 and even 4 the wrong side. Any chance these will work for curtain 2 instead of curtain 1 rather than having to unpick it all?! Whoops.

Thank-you in advance.

Caz

SewHelpful:  

I'm sorry without looking at it in front of us and knowing how many panels and  how many curtains etc we cannot say.

Sabina

Hello, could you please confirm I understood the process correctly?

These are my calculations:

- Fabric cut drop: 177.5 cm

- Half drop pattern repeat: 59cm

- ACD: 3.5

- 7 widths of fabric (for a pair of curtains)

As per your calculator, ACD (3.5) x half drop pattern repeat (59cm) = 206.5 cm

My query is:

Based on the above figures and calculations, do I need to cut the fabric every 206.5 cm 6 times? Then, when I have to cut the last width, will it be 206.5cm + 59cm long? Is that how it is supposed to work? The last width will be split in half and added to each curtain section.

Thanks a lot in advance,

Sabina

SewHelpful:  

Yes with those figures the drops are 206.5cm except the last one which is 206.5cm + 29.5cm. Note The 29.5cm is half the full pattern repeat. The other 29.5cm in the total is half a pattern repeat to position the fabric. 

Your figure of 59cm needs to be the whole pattern repeat. Also you will see in our tutorial videos that when cutting it is not the exact distance you need to cut (as the pattern repeat may be slightly different to the given figure), you need to cut the correct number of pattern repeats at the correct position on the pattern when cutting the drops.

Janet

Are we allowed to print this calculation, as I can not get it to print.

This calculator is so useful, Thank you.

SewHelpful:  

The page is not formatted for printing

Lulu

I am making a pair of double pinch pleat curtains for a rail that is 190cm + 10% spring back = 209cm.

Curtain cut height is 245cm. This fits exactly with the pattern repeat which is 98cm (1/2 drop) and allows plenty for hems and to cover the buckram.

What I am confused about is the horizontal pattern repeat is 86cm on a usable width of 130cm (out of 132 width).

Does that mean I only have 86cm usable width on each drop? Or do I assume that there are 1.5 horizontal pattern repeats and the adjusted A/B cut drops will line up.

I’d like the curtain to be appear full but can’t work out if 4 widths or 5 widths are required? I’m terrified of buying too little or way too much as the fabric is quite expensive. My brain is frazzled trying to work this out!

Thank you!

SewHelpful:  

Look at our article on HALF DROP PATTERN REPEATS EXPLAINED .

The fabric you describe sounds like a half drop pattern repeat and if the supplier is saying it is then I would expect to be able to use the whole width (1.5 horizontal pattern repeats) for joining.

The fact it is 1.5 horizontal PR across is what creates the half dropm pattern repeat. 1.5 x 86 = 129cm. Therefore I would expect the fabric to join every 129cm (not 86cm).

Your fabric cut drop is exactly 2.5 PR wich is good and bad. First it means you will have no wastage at all and therefore not waste any money buying fabric that will be trimmed off and not used.

You will not have any excess fabric though for timming the bottom square and dealing with a any potential issues with the fabric.  If you come up against these problems you would have to adjust the size of your hem.

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