Swimwear Calculator

Nylon/spandex blends (typically 80% nylon, 20% spandex) are the industry standard for swimwear. They offer excellent stretch recovery, resist chlorine reasonably well, and dry quickly. Look for fabric with at least 75% four-way stretch.

Polyester/spandex blendsare even more chlorine-resistant than nylon and hold colour better over time. They feel slightly different on the skin — less silky, more matte — but are the best choice for pool swimmers.

Avoid cotton or cotton blends for swimwear. Cotton absorbs water, stretches out when wet, dries slowly, and becomes transparent. It is unsuitable for any functional swim garment.

Always pre-wash your swim fabric in cool water before cutting. This removes manufacturing chemicals, tests for shrinkage, and ensures the fabric behaves as expected when you sew.

Swimwear elasticis specifically formulated to resist chlorine, salt water, and UV exposure. Regular elastic (woven or knit) will degrade rapidly in pool water — the rubber breaks down and the elastic loses its snap within a few wears.

Clear elastic(transparent polyurethane) is sometimes used at necklines and armholes where you want stretch without visible bulk. It has very high stretch, so cut it to 70–75% of the opening measurement.

Fold-over elastic (FOE)wraps around the raw edge for a clean finish on leg openings and necklines. It’s available in chlorine-resistant versions specifically for swimwear. Cut it to 75–80% of the opening.

Always test elastic stretch recovery before committing. Pull a short length to 150% for five seconds and release — it should snap back fully. If it stays stretched, it’s degraded or poor quality.

Every swimsuit needs lining — without it, the outer fabric becomes transparent when wet. Cut lining pieces to the same dimensions as the outer fabric (same negative ease applied).

Power meshis a popular lining choice for areas that need support (bust, seat). It’s sheer but provides compression and structure. Use nude or skin-tone mesh for the most invisible result.

Swim lining(a lightweight nylon/spandex) is used for full-body lining. It matches the stretch of the outer fabric and dries quickly. Avoid using non-stretch lining — it will restrict movement and pull the suit out of shape.

Sew the lining to the outer fabric wrong sides together before applying elastic. This traps the raw edges inside and gives the suit a professional finish. For bikini tops, the lining also prevents the cups from being see-through.