Quick answer: For leggings, aim for 230–300 GSM in a 75–80% nylon / 20–25% spandex (or 94/6 seamless) blend with 4-way stretch. Heavier = more squat-proof and sculpting; lighter = more breathable.
At a glance
| Weight class | GSM | Typical use |
|---|---|---|
| Light | 140–180 | Tops, layering, hot-weather |
| Mid | 180–240 | Everyday leggings, sets |
| Heavy | 240–300+ | Compression, sculpt, opacity-critical |
What does GSM mean?
GSM = grams per square metre, the weight of the fabric. It's the single biggest lever for how activewear feels and performs. Light fabrics breathe and drape; heavy fabrics compress, sculpt and hide.
GSM by product
- Leggings: 230–300 GSM. Below ~220 risks see-through; 260–300 is the premium "buttery, squat-proof" zone.
- Sports bras: 220–280 GSM depending on support.
- Tops & tanks: 180–240 GSM for breathability.
- Seamless sets: typically 280–300 GSM, 94/6 polyamide-elastane.
Composition: nylon vs polyester, and spandex
Nylon (polyamide) is softer, more durable and has that "buttery" handfeel — the premium choice for leggings and sets. Polyester is cheaper, dries fast and takes sublimation print well — common for training tees and printed styles. Spandex (elastane) at 6–25% gives the stretch and recovery. More spandex = more compression and snap-back.
What makes leggings "squat-proof"?
Three things: enough GSM (260+), a tight knit, and the right fabric tension at the seat. Thin or low-tension fabric goes sheer when stretched. A good factory squat-tests every fit sample under bright light — always ask for this.
Finishes that sell
- Brushed / "naked feel": peach-skin softness, hugely popular.
- Ribbed: texture + gentle compression, on-trend for sets.
- Matte vs shine: matte reads premium; shine reads sport.
- Recycled (GRS): recycled nylon/polyester for sustainability claims.
GSM by garment, at a glance
| Garment | Typical GSM | Why |
|---|---|---|
| Summer tees, tanks | 160–200 | Airflow beats opacity needs |
| Everyday leggings | 200–230 | Balance of drape and coverage |
| Squat-proof leggings | 220–260 | Cover factor under 70% stretch |
| Sports bras | 230–280 | Compression zones need mass |
| Winter / brushed | 260–320 | Loft and warmth |
GSM (grams per square meter) is mass, not quality — but within one fabric family it is the honest signal of how much yarn you are buying. Two "buttery" leggings at 190 vs 240 GSM are different products with different squat-test outcomes and different prices, whatever the product page says.
How to read a fabric spec sheet
Five lines matter. Composition ("75% nylon 25% spandex") — fiber sets hand-feel and print compatibility. GSM — verify against the table above for the garment's job. Gauge/knit type — higher gauge means finer loops and smoother face. Stretch and recovery percentages — recovery under 90% will bag at the knees within weeks. Finish — brushed, matte, sheen; matte hides body-contour highlights, sheen amplifies them. If a supplier's spec sheet is missing GSM or recovery, that is not an oversight — ask, and get it in writing on the PI.
Verify on delivery: the cut-and-weigh
GSM is the easiest spec to silently downgrade and the easiest to check. A GSM cutter (a $30 circular die) punches a 100 cm² disc; weigh it on a jewellery scale, multiply by 100. No cutter? Cut exactly 10×10 cm, same math. Test three spots away from hems, after conditioning the fabric a day at room humidity. More than ±5% below spec on the bulk lot is a claim, not a shrug. We weigh every incoming lot as part of inline QC — the practice belongs in your inspection checklist too, next to the squat-proof protocol.
The two-axis map: GSM × stretch
GSM alone doesn't define a fabric — pair it with stretch-and-recovery and you get the real map. High GSM + high recovery = compression territory (squat-proof bottoms, support bras). High GSM + moderate stretch = structured winter knits. Low GSM + high stretch = second-skin summer layers that must never be asked to be opaque under load. Low GSM + low stretch = flowy overlayers. Most fit disasters are two-axis errors: a beautiful 200 GSM fabric asked to do a 240 GSM compression job. When you brief a factory, give the job description ("squat-proof high-rise, matte, buttery hand") and let the two axes be engineered together.
Planning GSM across a seasonal line
A coherent collection walks a deliberate GSM ladder: summer capsule at 160–200 (tanks, shorts, light leggings), core year-round at 220–250 (the squat-proof workhorses), winter at 260–320 (brushed leggings, half-zips). Two practical rules: keep each fabric family serving at least two styles so dye lots consolidate, and never let marketing name two different weights the same fabric name — "CloudSoft" meaning 190 in shorts and 240 in leggings will earn you a "quality dropped" review the first time a customer owns both. The pricing page shows how fabric choices map to program tiers.
FAQ
What GSM is best for leggings?
230–300 GSM. 260–300 for premium squat-proof compression; ~230 for lighter, breathable styles.
What's the best fabric blend for activewear?
75–80% nylon / 20–25% spandex for cut-and-sew, or 94/6 polyamide-elastane for seamless. Polyester blends for printed training wear.