What makes a fabric suitable for swimwear?

A swimwear fabric has to perform in conditions that would ruin most other stretch fabrics within a season. Pool chlorine is chemically aggressive — it breaks down elastic fibers, fades color, and causes fabric to lose its stretch and recovery. Saltwater, sunscreen, and prolonged UV exposure add to this. A fabric that works beautifully for leggings may start sagging and fading after a few months in the pool.

Genuine swimwear-grade fabric is selected specifically for four properties: chlorine resistance, UV stability, wet opacity (it shouldn't go sheer when the fabric is soaked), and fast drying. It also needs 4-way stretch — the ability to extend both lengthwise and widthwise — and strong recovery so the garment springs back to its shape after every stretch.

All the swimwear fabric on this site meets those requirements. The choice you'll make is between nylon and polyester, which weight to use, and whether you need a lining fabric alongside your outer fabric.

Nylon vs polyester for swimwear

This is the first decision most people making swimwear need to make. Both fabrics work well for swimwear. They have different strengths, and the right choice depends on how the swimwear will be used.

For a fashion swimsuit, resort wear, or a bikini that will be worn recreationally — pool days, beach trips, general summer use — nylon spandex is the better choice. The softness and colour depth make a noticeable difference in the finished garment.

For competitive swimmers, triathletes, or anyone spending hours in a chlorinated pool most weeks, polyester spandex (or a poly/PBT blend) is the more practical choice. It simply holds up longer under heavy chemical exposure. Read the full nylon spandex fabric guide if you want a deeper comparison of how both fibers perform across different applications.

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Chlorine resistance explained

Chlorine damages stretch fabrics by attacking the elastic fibers — the spandex component — in the blend. Over time this causes the fabric to lose its stretch and recovery, go baggy, and fade. The outer nylon or polyester fibers are more resistant, but the spandex content is vulnerable.

Nylon spandex handles recreational chlorine exposure well. A swimsuit made from good nylon spandex, rinsed thoroughly after each pool use and washed cold, will hold its shape through a full season of regular use. For someone swimming an hour a day, five days a week in a heavily chlorinated competition pool, polyester spandex or a poly/PBT blend is the better choice — polyester's molecular structure resists chlorine breakdown more effectively than nylon.

The single most effective thing you can do to extend the life of any swimwear, regardless of fabric, is to rinse it in cold fresh water immediately after leaving the pool. Chlorine left in the fabric continues to degrade the fibers after you're out of the water. A thorough rinse removes the chlorine before it can do further damage.

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UV protection in swimwear fabric

UPF (Ultraviolet Protection Factor) measures how much UV radiation a fabric blocks. A UPF 50 fabric blocks 98% of UV rays. For swimwear worn in intense sun — rash guards, surf suits, long-sleeve swim tops — UPF rating matters significantly.

Most swimwear-grade nylon and polyester spandex provides reasonable UV protection at standard weights simply because of the tight knit structure and fiber density. The higher the GSM, the more protection — a heavier fabric has fewer gaps for UV to pass through. A 160 GSM swimwear fabric will offer more UV protection than a 130 GSM fabric at the same fiber blend.

For garments where UV protection is the primary requirement — a long-sleeve rash guard for a child, a surf shirt for all-day outdoor use — look for fabrics specifically rated UPF 50+. Polyester tends to offer better inherent UV stability than nylon because its molecular structure absorbs UV radiation more effectively.

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Choosing the right weight (GSM) for swimwear

GSM — grams per square meter — is the single most important specification after fiber content. It determines how opaque the fabric is when wet, how much structure it provides, and how it drapes and moves. Getting the GSM wrong is the most common cause of a finished swimsuit that doesn't look right.

For most home sewists making a bikini or standard one-piece, a swimwear fabric between 140–165 GSM gives you the right balance of stretch, coverage, and movement. See the full fabric weight guide for a broader breakdown across all garment types.

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Swimwear lining fabric

Most swimwear — particularly one-pieces and bikini bottoms — benefits from a lining. The lining adds opacity, improves the way the garment sits against the body, and prevents the outer fabric from being the only layer against the skin in sensitive areas.

The standard lining for swimwear is power mesh — a lightweight, open-knit nylon spandex fabric that's strong despite being thin, stretches easily in all directions, and dries extremely fast. It adds almost no visible bulk but makes a significant difference in how the finished swimsuit wears and feels.

A denser swim tricot lining (around 100–120 GSM) adds more coverage and opacity. This is the right choice for lined one-pieces, tummy-control panels, and anywhere you want the lining to contribute meaningfully to the structure of the garment.

Browse the swim mesh and lining fabric collection, or read the swim mesh lining guide for a full breakdown of lining types and how to use them.

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Fabric for specific swimwear styles

Bikinis and two-piece swimsuits

Bikinis need fabric with enough stretch to move comfortably without riding up, enough recovery to spring back after every movement, and enough opacity to hold up when wet. A 130–155 GSM nylon spandex is the right choice for most bikini styles. Printed nylon spandex works beautifully for fashion bikini tops and bottoms — the wet printing process produces sharp, detailed patterns that don't fade or distort when the fabric stretches. Browse the printed spandex collection for current pattern options.

One-piece swimsuits

One-pieces carry more tension across a larger piece of fabric and need to hold their shape through more demanding movement. A 150–170 GSM fabric gives you the structure for a one-piece that holds its line without restricting movement. For swimsuits with built-in support cups or tummy-control panels, use a denser fabric for the structured panels (170–200 GSM) and a more pliable fabric for the rest of the suit. Line the torso section with swim mesh for added support and opacity.

Rash guards and swim shirts

Rash guards need to cover skin and provide UV protection without restricting paddling or swimming motion. They're also worn for extended periods in strong sun. For this reason, polyester spandex is often the better choice for rash guards — its UV stability and chlorine resistance hold up better for active outdoor water use. A weight of 170–200 GSM provides the coverage needed for meaningful UV protection. Use 100% polyester thread for all construction on any garment that will see heavy chlorine or UV exposure.

Boardshort lining

The inner lining of boardshorts needs to be light, fast-drying, and non-chafing. Power mesh at 80–100 GSM is the standard — it dries in minutes and moves freely without bunching. It also doesn't hold water weight, which matters for surfing and water sports. See the mesh lining fabric guide for construction details.

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How many yards of fabric do you need?

This is a question with a range rather than a fixed answer — it depends on your pattern, your size, and how you lay out the pieces. These are practical starting estimates, not exact numbers. Always add at least 10–15% extra to account for cutting errors, fitting adjustments, and directional prints.

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Sewing swimwear fabric — what you need to know

Swimwear has a few specific construction requirements that differ from regular stretch sewing. Getting these right makes the difference between a swimsuit that falls apart after a season and one that holds up for years.

Thread

Use 100% polyester thread for all swimwear construction. Cotton-blend thread deteriorates quickly when exposed to chlorine and saltwater — seams that look fine on day one will start popping within a season. Polyester thread resists chemical degradation and has a small amount of stretch, which helps it flex with the fabric. For serger loopers, wooly nylon thread produces the softest seam allowances and good stretch coverage.

Needles and stitches

A ballpoint or stretch needle (size 75/11 or 80/12) prevents the needle from perforating the knit fibers. A standard sharp needle causes runs in stretch fabric. Use a stretch stitch or narrow zigzag (approximately 1mm wide, 2.5mm long) for all construction seams — a straight stitch has no flex and will pop when the fabric is worn. On a serger, a 4-thread overlock is the standard construction stitch for swimwear.

Elastic

Use swim elastic or chlorine-resistant elastic for waistbands and leg openings. Standard braided elastic degrades quickly in chlorinated water and will lose its stretch within a few washes. Clear swim elastic or rubber elastic holds up significantly longer. This is one of the most overlooked details in home swimwear sewing and one of the most common reasons finished swimsuits fail prematurely.

For a complete guide to needle selection, stitch settings, and seam construction for stretch fabrics, see how to sew stretch fabric.

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Caring for swimwear fabric

The care habits you build around swimwear extend its life more than any other single factor. The most important steps happen immediately after you leave the water.

Rinse immediately after pool use. Don't wait until you get home. Chlorine left in the fabric after swimming continues breaking down the elastic fibers. A thorough rinse in cold fresh water removes the chlorine and stops the degradation.

Hand wash or use a gentle machine cycle, cold. Hot water accelerates the breakdown of spandex fibers. A mild detergent is fine. Avoid fabric softener — it coats the fibers and reduces the fabric's ability to dry quickly and maintain its stretch recovery.

Air dry flat. Hanging a wet swimsuit can stretch the fabric under its own weight while it dries. Flat drying on a towel maintains the garment's shape. Never tumble dry swimwear — the heat permanently reduces elasticity.

Don't store a wet swimsuit balled up. Rinse, dry, then store clean. Leaving damp swimwear in a bag for hours allows chlorine and bacteria to continue breaking down the fibers.

For full care instructions across all stretch fabric types, see the fabric care guide.

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Frequently asked questions