Why one number gets so much attention
When buyers compare legging fabrics, the spandex share is usually the first number they look for. That makes sense. Spandex is the elastic fiber that lets a knit stretch in every direction and snap back. Without enough of it, yoga pants bag at the knee and slip at the waist. With too much, they can feel tight and warm for slow or long sessions.
But the number does not work alone. The same spandex share behaves differently in a light jersey and a heavy interlock, and in nylon versus polyester. This note explains what the common percentages change and how to read them together with weight and knit.
Three reference points
| Spandex share | How it usually feels | Where it fits |
|---|---|---|
| About 15% | Comfortable stretch, light hold | Everyday and slow-flow pants, relaxed sets, tops |
| About 20-24% | Supportive, sculpted, stays in place | Core studio leggings in nylon interlock (75-80% nylon) |
| 25% and above | High compression, firm hold | Training leggings and compressive styles |
These are reference points, not rules. Two fabrics with the same spandex share can feel different because of yarn count, knit tightness and finishing. The fabric sheet should state the exact composition the mill confirms, and the feel should be approved on a swatch and then on a sample.
Around 15%: comfort first
At about 15% spandex, a fabric has enough stretch to move with the body without pressing on it. This suits yoga pants for slow flow, restorative classes and all-day wear, and it suits tops where hold is not the goal. The trade-off is that recovery and hold are lighter, so waistbands and seat areas rely more on construction, such as a taller or layered waistband, to stay in place.
Around 20-24%: the studio middle
Most performance studio leggings sit in this band. Typical interlock sheets read 75-80% nylon and 20-25% spandex, and brushed versions are often around 76/24 or 78/22. At this level the fabric holds the shape of the legging, recovers well after deep bends and stays opaque under tension for its weight. For most first collections this is the safe starting point.
25% and above: compression
Above about 25% the fabric starts to feel compressive. Customers who like a firm, held feel for training or power classes may want this. Others will find it warm and restrictive for long holds. If your line includes a compressive style, label it clearly as such in product copy, and avoid any body-shaping or medical language. Describe hold and support, not results on the body.
The weight trap
The most common mistake is to read weight and spandex share separately. A heavy fabric with only 8-10% spandex can look substantial on paper and feel stiff and boardy in a forward fold. The weight gives it opacity, but there is not enough elastic fiber to let it move comfortably.
Our GSM guide covers weight in more detail, including how weight relates to opacity in light colors.
Recovery is what customers notice
Customers rarely know the spandex percentage, but they notice recovery. Recovery is how completely a fabric returns to its original dimensions after being stretched. Poor recovery shows up as baggy knees, a loose seat and a waistband that rolls by the end of a class.
Spandex share is one input to recovery, but knit structure and heat setting at the mill matter too. That is why recovery should be measured, not assumed. ASTM D2594 is a test method for stretch and growth of knitted fabrics, and it gives a written result you can compare across fabric options and between production lots. See stretch and recovery testing for how to set acceptance with your lab.
Spandex across the rest of the line
- Sports bras: spandex share works with band construction and cups to set support. Confirm the composition on the fabric sheet and judge support on the sample, not on the number alone. Our sports bras guide covers support levels.
- Shorts: similar to leggings, but leg openings ride up more readily with high spandex and a light fabric. Hem construction matters as much as the fabric.
- Loose pants and tops: relaxed silhouettes need little hold. Lower spandex or none at all is common in cotton, modal and viscose fabrics.
- Seamless styles: stretch comes from yarn and knit program rather than a roll specification, so compare seamless samples on feel and recovery rather than on a single percentage.
Labeling the spandex share
In the US, fiber content appears on the label by percentage under the Textile Fiber Products Identification Act (16 CFR 303), together with country of origin and dealer identity. The percentages on your label should match the composition the mill confirms for the production fabric, not a rounded marketing figure. If you change fabric between seasons, update the labels at the same time. Avoid using trademarked fiber names on labels or product pages unless you have the right to use them; the generic name spandex or elastane is the safe choice.
Caring for spandex
Spandex is sensitive to heat. High dryer temperatures and hot irons can weaken it over time and reduce recovery. Write care instructions that match how the fabric was tested for dimensional change, for example to AATCC 135, and keep the care label consistent with the hang tag and product page. A care label that says one thing and a product page that says another causes returns.
How to choose for your program
- Write down the practice and the feel you want: easy comfort, studio hold or compression.
- Pick a starting spandex band from the table above and a weight range that suits your colors.
- Request two or three finished swatches across that band so you can compare side by side.
- Approve the fabric sheet with composition, finished GSM and a recovery test method.
- Judge the sample on a fit model through a full range of poses, including deep flexion.
The fabric library lists the common qualities by spandex band, and the leggings guide shows how fabric choices combine with waistband and gusset construction. When you have a shortlist, send it to the desk.