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Tips & Techniques > Substition formula woven <-> stretch fabric

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Posted by: Agnes

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Member since: 11/16/02
Reviews: 26 (tips: 2)
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Posted on: 11/6/05 1:16 PM
Review Rating: Helpful by 4 people   Very Helpful by 31 people   
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For a while I've been looking for information about how to adjust a pattern for woven fabric for stretch.
The general advice seems to be to make the pattern in a smaller size, but since all depends on the amount of stretch in the fabric used I didn't feel very comfortable with this.
I really was looking for some kind of formula that would take the amount of stretch in the fabric into account.
When I ran into the same problem whilst making a pattern in PMB 3 I decided to contact their helpdesk (after all they do also make PMB curves that does allow you to make adjustments for stretch). The helpdesk got back to me with the formula I was after and I thought I might be usefull for others. I know the subject has come up lots of times on the messageboards.

The formula:
Determine the stretch-factor of your fabric
Fold the fabric on the crosswise or lengthwise grain, several inches from the cut edge or selvage. Measure 4" of the fold, then stretch. If it stretches to 5", it has 25% stretch; if it stretches to 6", it has 50% stretch; etc.

This way you'll end up with a horizontal and vertical stretch factor. The vertical one is only used to make things like swimsuits, stirrup-pants,etc.

So you take the horizontal stretch factor and use this formula:

Adjust your base pattern to zero ease in the areas that are close fitting.
Then you scale between 1 and 3 percent > for each 10 percent of stretch. For example lets say the fabric has 30 > percent across stretch. Using 2 you would scale 6 percent. So you need to scale the width of the patternpieces down by 6%.

What makes you choose either 1,2, or 3 scale is how close fitting the garment has to be. For example 3 is used for swimsuits.

I made a pair of pants using this rule (scaling by 2) and they came out great!

I hope this makes sense, it's a lot easier to do then to try and write it down!

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cascadia said... (9/27/16 at 4:13 AM) Reply
I've asked about this in various places many times. I knew there had to be a formula somewhere - how else would pattern drafters and manufacturers do it, right? They wouldn't just guess. I'm wondering how much you'd multiply the body measurements by to make shapers or a sports bra or compression leggings that have to be very tightly fitted. Probably more like 10-15%. So like a 50" hip, the pattern would be drafted for a 42-44" hip or something.
Agnes said... (11/10/05 12:14 PM) Reply
Hmm... I don't know about knowledgeable. I just like to know how things work and why things work and like to know what I'm doing and not just guessing or winging it. Call me a nerd...... The reason for really wanted to know this particular formula is that I had a really hard time to find non-stretch woven fabric. Even the beautiful italian wools I've bought recently al got some stretch in. About trying the formula've got the exact same idea as I had. I haven't tried it yet, but will very soon. I wanted to make some lingerie, but only have patterns for stretch fabric lingerie. No I've got some beautiful non stretch lace, so that will be my first attempt. Because thinking logically if it works one way it should work the other way around as well. I think you'll have to take into account that you will have to add some wear-ease. This formula's starting point is no-ease-patterns wich is fine in stretch, but when you would use this formula to change the pattern for a woven fabric you would have a tight fitting woven garment, wich wouldn't give you much room to move. These are just my thougts, there are a lot of people here with a lot more knowledge on this subject, who might want to give their expert opinion....
FeyFaerie said... (11/9/05 2:19 PM) Reply
Hi Agnes! Great info.! Your instructions are very clear and concise. It sounds like you work with a lot of stretch knit fabric/patterns... so, Do you think that by calculating backwords I could take a "stretch fabric" pattern and adjust it for wovens? -I understand that the "stretch" factor would have to be conservative. - I've seen a lot of cute "stretch only" patterns out there, that I think would be really cute in a crisp cotton, blend, or even silk dupoini! You seem very knowledgable, and after working with this formula, I thought you might have a "feel" for this "backwords" calculation theory. Any suggestion/s you might have would be great! Thanks again for the information and the "formula"!
Karla Kizer said... (11/7/05 4:22 PM) Reply
You mean there's a method? It isn't just hit or miss? Very interesting...thank you!
zoezmommy said... (11/7/05 8:56 AM) Reply
very helpful..thanks for posting!
thaiyal said... (11/7/05 7:54 AM) Reply
I got it! Thank you :) I was wondering what if I use woven for a pattern meant for knit and vice versa.
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