The most important thing to know when sewing with knit, stretch or woven stretch fabrics is the percentage of stretch of the fabric.
Often the stretch percentage is not provided at discount fabric stores, or you may forget to look on the bolt. Even at high end fabric stores, often the stretch percentage is not provided and you’ll need to be able to determine this yourself in order to create a successful sewing project.
This is particularly the case when. you purchase fabric during a sale, bring it home and months later try to match up your fabric to a pattern.
Understanding Stretch Percentage
Stretch percentage refers to how much a fabric can stretch beyond its original length.
Wovens have a slight stretch along the bias. Obviously, you don’t calculate the stretch where there is none.
Knit fabrics are known for their stretchiness, making them ideal for projects like t-shirts, leggings, and other form-fitting garments. However, not all knit fabrics have the same amount of stretch, so it’s important to know the stretch percentage before starting your project.
You’ll need to be sure if your fabric has the matching requirements for your sewing project.
Often you need to know what the percentage is to create a bias neckband or binding tape for a neckline or armhole. See our article on the differences between bias neckband and binding tape.
Mathematically speaking, to calculate the stretch percentage you take the length of your fabric when stretched, less the original length, divide it by the original length, and then multiply by 100. But if you are like me, you’ll need to have a bit more backstory about stretch fabrics and you’ll also benefit from seeing a short video.
Let’s take this a bit further…
Directional Stretch
Stretch percentage can vary depending on the direction in which the fabric is stretched. There are two main directions to consider: across the grain (also known as horizontal stretch) and along the vertical (also known as lengthwise stretch).
Horizontal stretch runs perpendicular to the selvage edge of the fabric, and it’s what allows the fabric to stretch around the body. Lengthwise stretch runs parallel to the selvage and determines how much the fabric can stretch up and down.
Determining Stretch Percentage
To calculate the stretch percentage of a knit fabric, you will need to measure how much the fabric stretches beyond its original length. First, measure the length of the fabric without stretching it. Then, stretch the fabric as far as it will comfortably go and measure the length again. Subtract the original length from the stretched length, divide by the original length, and multiply by 100 to get the stretch percentage.
For example, if your fabric originally measures 10 inches and stretches to 14 inches when pulled, the calculation would be:
(14 – 10) ÷ 10 x 100 = 40% stretch
If you’re still unsure about how to determine stretch percentage, check out this helpful video tutorial:
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