Thursday Tip with Hali - Calculating stretch percentage
Thursday Tip // Calculating Stretch Percentage
“Stretch percentage” in sewing is typically associated with knit fabrics (there are stretch wovens too!) and refers to the amount of stretch the fabric has, either vertical stretch or horizontal stretch. Vertical stretch refers to the amount of stretch along the grainline (parallel to the selvedge) and horizontal stretch refers to the amount of stretch along the crosswise grain (perpendicular to the selvedge). The diagram below shows the directions of stretch on a swatch of fabric. Feel free to save it or pin it for future reference!
ID: a pink swatch of organic cotton jersey fabric (magenta) lying on a cutting mat. Directional arrows indicate grainline, crossgrain, bias and selvedge.
Stretch percentage can be calculated in several ways with similar mathematical equations but sometimes math is intimidating! Hopefully we can present you with a simple way of calculating stretch percentage that doesn’t involve too much math.
What is 2-way stretch and 4-way stretch?
It is also common in fabric listings to see the stretch percentage described as “2-way stretch” or “4-way stretch”. “2-way stretch” is just referring to the horizontal stretch (The fabric will only stretch along the horizontal/crosswise grain but NOT the lengthwise/vertical grain). “4-way” stretch means the fabric will stretch along BOTH the horizontal/crosswise grain and the vertical/lengthwise grain.
The “2-way” terminology likely comes from the idea that the fabric stretches to the left and to the right along the crosswise grain. And the “4-way” stretch refers to the fabric stretching in all directions, both left and right, up and down (think North, east, south, west). Don’t ask me why it’s overcomplicated like this, it’s just one of those things that someone decided was a good idea and now we go with it.
How to measure stretch percentage:
Take a 4” swatch of fabric or a larger piece of your fabric and fold it along the crossgrain. It is not necessary to cut a swatch but if you have one handy then either works.
To check horizontal stretch: Fold your fabric along the crossgrain and pinch a 4” section between your fingers. If you are using a 4” swatch then pinch each end.
Take a ruler or use a cutting mat and find the “0”.
Hold your left hand at zero and your right hand at 4 inches. Consider this 4” section of fabric to be 100%, where each inch is 25% of the total 100% of fabric.
Holding your left hand steady at zero, pull on your fabric with your right hand as far as it will stretch.
If your fabric stretches to 5” then it has 25% stretch. Meaning the fabric was able to stretch 25% more than its original size (so 125% in total or 1.25 times more than the original size). If it stretches to 6” then it has 50% stretch and so on.
To check the vertical/lengthwise stretch, fold your fabric parallel with the selvedge along the lengthwise grain and follow steps 2-5 in the same way.
Picking a fabric based on stretch percentage:
It is important to consider the stretch percentage when picking fabric for a pattern. Most patterns will indicate the stretch % needed for a particular pattern, however they often give a slight range (eg. 10-20% stretch) so it is good to understand the difference stretch % can make on the overall fit and look of your garment.
If you choose a fabric with less stretch than the pattern calls for you may want to consider sizing up so you still have enough ease to move comfortably and put the garment on. Similarly, if you choose a fabric with way more stretch than the pattern calls for you may want to consider sizing down as the garment may fit more oversized than intended because of the added stretch.
Direction Of Greatest Stretch (DOGS):
Also consider the direction of greatest stretch (DOGS) when cutting out your pattern pieces. For most knit garments you will want the direction of greatest stretch to wrap around the body to allow for the right amount of ease. If you cut your pieces out on the incorrect grain you may have more difficulty putting the garment on because it won’t have enough stretch to get over your shoulders or above your hips etc. You may also notice the garment start to succumb to gravity as the sleeves lengthen and the hem starts to droop over time. Before I knew this could happen I cut a pair of sweatpants on the wrong grain and over time they have grown about an inch in length as I’ve worn them. Lesson learned.
So keep these things in mind when choosing your fabric based on stretch percentage. Also, check out our current selection of knit fabrics here! We always try to include the stretch percentage in our listings and it is also included on our fabric sample cards.
Let us know if you have any questions by putting them in the comments or sending us an email. We would love to hear from you!