What is stretch percentage of knit fabrics?
Stretch percentage is the amount of stretching of knit fabrics. Knowing the stretch percentage of knit fabrics is essential for pattern drafting for knits, as well as sewing with knit patterns.
You can find the skill of measuring the stretch percentage very useful when drafting your own patterns, adjusting a pattern to fit with the fabric you want to use or even when you're shopping for fabric to follow the recommendations in commercial patterns.
Most knit fabric stretch, no matter if there is a lot of spandex in them or no spandex at all. This is in result of the way the knit fabric is constructed. Knit fabrics with no spandex added stretch just a little bit. When there is spandex added to the structure of the fabric, knits can stretch up to 100% in both directions.
Many sewing patterns for knits, including SewingForALiving ones, have negative ease added to the measurements. This means that the final garment will actually be smaller than the body measurements. That's why it is important to follow the pattern recommendations for fabric stretch so that the garment can fit nicely.
Knit fabrics can be 2-way and 4 way stretch. 2- ways means that fabric stretches across the grain, from selvage to selvage. 4-way stretch means that the fabric stretches in both directions - with and across the grain.
Usually, knits have the greatest stretch across the grain. This is the direction pattern details are laid out so that the fabric stretches across the body. That's why we usually measure stretch percentage across the grain.
Some patterns ask for 4-way stretch of the fabric. If this is the case, you will have to measure in both directions.
Types of knits according to their stretch percentage
According to the stretch percentage, knits can be:
1. One-way stretch stable knits with 0% - 25% stretch.
This type of knits stretch very little and they can be treated almost like woven fabrics in terms of pattern reduction and wearing ease.
2. Moderate knits that stretch up to 50%.
Examples for knits with moderate stretch are most jersey knits, interlocks and T-shirt knits.
3. Stretchy knit that stretch 51% to 75%.
Examples for stretchy knits are some jerseys and T-shirt knits as well as velour and stretch terry.
4. Super stretch knits that stretch from 76% to 100%
These are fabrics that are suitable for leotards, leggings and swimwear. Examples are 4-way spandex and supplex fabrics.
For each of the stretch factor groups above, there is a different percent of pattern reduction that we need to make in order to fit the pattern accordingly. This means that we need to subtract some inches/centimeters from the body measurements to make the pattern fit.
One-way stretch stable knits with 0% - 25% stretch don't need pattern reduction. Moderate knits need 2% pattern reduction, stretchy knits need 3.5% and super stretch knits need 5%.
How to measure the stretch percentage of knits?
To find out the stretch percentage of knit fabrics, fold the fabric on crosswise grain, measure 4 inches and pull the fabric as long as it would go. Every half an inch it stretches over the for inch mark corresponds to 10% of stretch.
Here is a printable ruler you can use to determine the stretch of knits. Make sure to print in actual size.
Download The Printable STRETCH PERCENTAGE RULER GUIDE In Inches And Centimeters
Set the printer to actual size and set the scale to "none". The ruler prints on A4 and US letter size paper.
A regular ruler will do the job as well, just measure how much the fabric stretches and count every ½ inch over the 4" for 10% of stretch.
If you measure in cms, every centimeter over 10 will correspond to 10% of stretching. For example, if the fabric stretches to 12 cms, the fabric has 20% stretch.
Recovery of Knit fabrics
Another thing that you might want to pay attention to is the recovery of the fabric after it has been stretched.
When you stretch the fabric as much as it would go to determine the stretch factor, it bounces back to take its original shape. The fabrics that bounce back close to their original shape have good recovery.
Fabric with more spandex in their content tend to have better recovery than the ones with less or no spandex in their composition.
You can use them for sewing really fitted garments like leggings or bathing suits, because the garment is going to keep its shape after the intensive stretching when you wear it.
There are garments that don’t need very good fabric recovery as well as garments for which good recovery is essential.
Therefore, you need to consider fabric recovery together with the stretch factor when picking the fabric for a sewing project.
Here is a video on how to use the stretch and recovery percentage ruler.
After you measure the stretch percentage and recovery of fabric, you can go ahead and decide on the percentage of pattern reduction for knit patterns. This is also called adding negative ease to the pattern.
Here are some more recources you might want to consider regarding pattern drafting for knits and pattern reduction:
Patternmaking For Knits: Essential slopers at Craftsy which you can watch as part of Craftsy unlimited with a free trial and
where you can get your first class 20% off with coupon LEARN2SEW.
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