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How to calculate stretch percentage (with FREE print at home stretch percentage guide!)

In my sewing patterns created for stretch fabrics i often talk about the required fabric in terms of stretch percentage. For example, in the Briar tee pattern i say that you need to use a fabric with at least 20% stretch. For my maternity patterns i generally suggest fabrics with at least 40% stretch.

I feel like this is the best way of explaining exactly how stretchy your fabric should be to work with the design, but i know that if you’re not familiar with that measure it can be a little confusing. Thankfully it’s really really simple to calculate! I’ll show you how to calculate it yourself, and at the end of this post you’ll be able to download our free print at home stretch percentage guide.

How to calculate stretch percentage with FREE print at home guide!

Your stretch percentage is just the width of your fabric when stretched to it’s maximum divided by the width of your fabric when unstretched (minus 1).

For example in the example shown below the stretch percentage would be 16/10-1 = 0.6 . This means the stretch percentage is 60%.

I find a very simple and quick way to calculate stretch percentage without a calculator is to keep the fraction simple. So I take a swatch of fabric and hold it width ways next to a ruler, tape measure or cutting mat, with my fingers placed at 0 and at 10 (it doesn’t matter if you’re using CM or inches, 10 is just a very easy number to use mentally). I leave my left hand static and stretch the fabric held by my right hand. That way i can very easily read off the number and mentally calculate the percentage.

So again with my example below, i can see at a glance that the stretch percentage is 60%.

2015-08-02-stretch-percentage2

One of the reasons i love talking about stretch percentage rather than the specific fabric content in our pattern requirements, is that it makes it easier to understand how you can manipulate the fit of your garment.

For example with the Briar, if you choose a fabric with a high stretch percentage, your garment is going to sit differently, more loosely. If you choose a fabric with a lower stretch percentage than required, it will fit more tightly and may be a little harder to get on and off. With the Briar this isn’t a big deal since it’s quite loose fitting. I often use sweater knits that have a lower stretch percentage and just accept the fact that i will either need to size up, or they will fit a little more snuggly. But on the other hand, one of my most upsetting makes ever was when i sewed up a pair of Virginia leggings with a very comfy fabric and forgot to check the stretch percentage before sewing. I couldn’t get them on! Considering i was pregnant at the time it was really really upsetting (cue me freaking out about pregnant weight gain) until i realised that the fabric had only 10% stretch when i needed 40% hehehe

Lesson here: Always check your stretch percentage babes!

To download our super easy to use stretch percentage guide (which completely removes the need to calculate anything) just enter your email address below, and it will be emailed directly to you:

How to calculate stretch percentage with FREE print at home guide!

About Author

Meg is the Founder and Creative Director of Megan Nielsen Patterns, and is constantly dreaming up ideas for new sewing patterns and ways to make your sewing journey more enjoyable! She gets really excited about design details and is always trying to add way too many variations to our patterns.

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[…] with at least 40% stretch and this jersey only had 20%, i sized up. (More about stretch percentage in this post). Buddy is 5 and wear’s a size 4/5, so i cut the size 6/7 and made them a little shorter, as […]

Tamara Ross
Tamara Ross
4 years ago

I’ve been searching for some specific information about how to draft your pattern using the stretch factor. Otherwise, knowing you have a 60% stretch factor, where do you make those adjustments on the pattern and what are those adjustments? Any insight on how to apply the stretch factor to pattern drafting would be great! Thank you

Yvonne A MaLik
Yvonne A MaLik
3 years ago

Thank you so much this was very very helpful

Mia
Mia
3 years ago

Thank you. Just what I needed to know. After 30years of sewing clothing ( everything including wedding dresses ) I am only now venturing into knits ( yeah I know: unbelievable). Wanting to manage without a serger though.

Ann
Ann
3 years ago

I tried to download the printable stretch guide but got the error message “API key has been disabled”

Sirkka
Sirkka
3 years ago

I teied to download the stretch percentage guide an din not be able to do it. Some error accurred. Can you help? Please.

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[…] flags”.  The pattern states the fabric needs to have between 20% and 30% stretch. I used the Megan Neilsen guide  for calculating the […]

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[…] make the circle skirt I first worked out the stretch percentage of the fabric. The quickest way I do this is hold 10cm of fabric and see how far it stretches, for […]

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[…] If your pattern recommends a specific stretch percentage you can check out this handy-dandy blog post by Megan Nielsen Patterns, which will help you ascertain the stretch of the fabric you have on […]