Best Fabric for Gym Wear and Leggings

Fabric is the whole product in gym wear. A legging that goes sheer in a squat, a tee that holds sweat instead of moving it, a bra that stretches out after ten washes — none of that is a sewing problem. It is a fabric problem, decided before a single panel is cut. This is what we specify when brands come to us, and why.

The two blends that cover almost everything

Most activewear ranges are built on two fabrics. Get these right and you have covered the bulk of a collection.

Fabric	Typical blend	Use it for	Why
Nylon / spandex	75/25 to 80/20	Leggings, sports bras, premium sets	Softer hand, buttery surface, better recovery. The fabric brands charge a premium for.
Polyester / spandex	85/15 to 88/12	Performance tees, shorts, compression	Dries faster, costs less, takes sublimation print. Nylon does not sublimate well.

Nylon or polyester for leggings?

Nylon, if the legging is the product. It feels better against skin, holds its shape through more wash cycles and recovers better after stretching — which is what stops a waistband going slack by month three. Polyester is the right call when the legging is a supporting piece in a wider range, when the price has to come down, or when you want all‑over print, because polyester sublimates and nylon does not.

One thing buyers often miss: spandex content matters more than the base fibre for how a garment feels. At 12% you get stretch. At 22–25% you get compression and recovery. A 78/22 nylon legging and an 88/12 nylon legging behave like different products, and a supplier quoting you “nylon spandex” without the ratio has told you almost nothing.

The rest of the fabric list

Two blends cover the core, but a full range needs more. These are the ones that come up most often:

Fabric	Where it belongs	Watch for
Power mesh	Bra wings, support panels, ventilation zones	Specify the weight separately — light mesh gives no support at all
Brushed poly / spandex	Cold-weather leggings, winter tops	Brushing adds warmth and hides show-through, but pills faster
French terry / cotton blends	Joggers, hoodies, the lifestyle half of a range	Comfortable, but it is not training fabric — cotton holds sweat
Seamless knit	Bras, crop tops, premium sets	Knitted as a tube, so no side seams to rub. Higher MOQ and longer lead time
Recycled polyester (rPET)	Anywhere virgin polyester would go	Performs the same; costs a little more. Honest about what it does and does not fix — see below

Squat-proof is a weight question, not a fabric question

Sheerness under stretch is the most common complaint about own-brand leggings, and it is almost always under-specified weight rather than the wrong fibre. For leggings we would not go below 260 gsm, and 280–320 gsm is where the premium feel sits. Below about 240 gsm you should expect show-through on a deep squat, whatever the blend.

Construction matters as much as weight. Interlock and double-knit hide more than single jersey at the same gsm, because there are two yarn systems rather than one. Put the knit construction on the spec, not just a number.

Colour is the third variable nobody plans for. A light grey or pastel legging will show through at a weight where black is completely opaque, so test your lightest colourway, not your flagship black one. We sample the worst case deliberately for exactly this reason.

Sports bras

Same nylon/spandex family, usually a little heavier, often with a separate power-mesh or bonded panel for support. Seamless knitting earns its money here more than anywhere else in a range: no side seams means no rub under a strap on a long run.

Support level is a construction decision, not a fabric one. Low impact is a single layer with a wide band. High impact needs encapsulation, a bonded or moulded cup, and a band that is genuinely firm — which means a higher spandex content in the band than in the body. Specify the two separately.

What moisture-wicking actually means

It is a construction and a finish, not a fibre. Polyester and nylon are both hydrophobic — they do not absorb water, so sweat travels along the yarn to the surface and evaporates. Cotton absorbs it and holds it, which is why a cotton gym tee gets heavy and cold. Any supplier who calls a fabric “moisture-wicking” without naming the blend and the knit is telling you nothing.

Four-way stretch

Two-way stretches across the body. Four-way stretches across and along it, which is what you need for anything that has to move with a hip and a knee at once. For leggings, bras and compression, specify four-way and put it in writing — it is a real cost difference, so it is a real place for a supplier to quietly substitute.

Finishes worth asking about

• Brushed or peached — softer hand, more warmth, slightly more pilling
• Matte vs shine — a yarn and finish choice. Matte reads premium on leggings; shine reads sporty on shorts
• Antimicrobial — reduces odour retention, which is polyester's real weakness against cotton. Worth it on training tees
• UPF — comes largely from tight construction and dark colour; a supplier claiming UPF 50 on light open mesh is guessing

How activewear fails, and what causes it

Every one of these arrives as a customer complaint rather than a factory defect report, so it is worth knowing which decision caused it.

Failure	Usual cause	Fix at spec stage
Goes sheer in a squat	Weight too low, or single jersey	260 gsm minimum, interlock or double knit
Waistband rolls down	Band too narrow, or too little spandex in the band	Wider band, higher elastane, or a bonded band
Loses shape after a month	Low spandex, or poor recovery yarn	20%+ spandex and a recovery test on the sample
Pilling between the thighs	Brushed surface, loose yarn twist, abrasion	Ask for a Martindale pilling result
Holds odour	Polyester's known weakness	Antimicrobial finish, or shift to a nylon-rich blend
Colour bleeds in the wash	Dye not properly fixed	Colour fastness test before bulk
Shrinks or twists	Fabric not pre-shrunk or relaxed before cutting	Three-wash shrinkage test on the sample

What to test before you approve bulk

Four tests catch nearly everything above, and all four can be run on a sample:

• Shrinkage after three washes — not one; the second and third tell you more
• Stretch recovery — stretch to 50%, hold, release, measure what comes back
• Pilling (Martindale) — the single best predictor of how the garment looks at month six
• Colour fastness — to washing and to rubbing, both

Ask for these in writing with the sample. A factory that cannot produce them, or that offers reassurance instead of numbers, is telling you something.

Recycled fabric, honestly

Recycled polyester performs identically to virgin polyester in a garment — same wicking, same durability, same print behaviour — and costs a little more. It is a genuine reduction in new plastic and a reasonable claim to make.

What it does not fix is microfibre shedding in the wash, which is the same for recycled and virgin. If sustainability is central to your brand, say what rPET actually does rather than implying it solves everything; buyers in this category check, and an overstated claim costs more credibility than the fabric buys.

Fabric MOQ is not garment MOQ

This catches most first-time brands. Our garment minimum is 50 pieces per style, but fabric is woven or knitted in rolls, and a mill minimum for a custom colour is typically far higher than one style's worth. In practice that means:

• Stock fabrics in stock colours — available at 50 pieces, shortest lead time
• Stock fabric, custom dyed colour — possible, but the dye lot sets the minimum
• Fully custom knitted fabric — realistic at several hundred pieces and up, with three to four weeks added for development

For a first range, use stock fabrics and spend the budget on fit and finishing. Custom fabric is a second-order improvement that most customers cannot feel, and it is where early brands most often spend money they should have kept.

What this costs to make

Our published price for a seamless gym set — leggings and sports bra — is $15.00 per set at 50 sets, factory direct, with your own labels. Fabric choice moves that: nylon/spandex sits at the top of the range, polyester/spandex at the bottom. See full pricing for the rest of the range, or the MOQ calculator to model your own quantities.

Specifying it so you get what you asked for

• Blend and ratio — “nylon/spandex 78/22”, not “nylon mix”
• Weight in gsm — the single most useful number on the sheet
• Knit construction — interlock, double knit, seamless
• Stretch direction — four-way, stated
• Finish — brushed, matte, compression, antimicrobial
• Test results required — shrinkage, recovery, pilling, fastness

If you are not sure of the numbers, send a garment you already like. We will measure it and write the spec from the real thing, which is faster and more accurate than describing it in words. A tech pack helps, but it is not required to start — we build one from references.