07 Jul 2022 • • by Amy

How to Sew in Swim Elastic: Two Methods!


Our latest pattern, the Faye swimsuit, uses rubber swim elastic at the waist and leg openings. We use two different methods for sewing in elastic: the clean finish and the turned finish. The clean finish at the waist (and neckline of the top) is sewn first and then the turned method is used on the leg openings. When we made our reversible swimsuit we used this method on the legs as well so you can wear it on both sides. In this post we will show you how to use both techniques to sewn in elastic. We have a Youtube video at the end of this post if you prefer learning that way! If you are new to sewing swimwear we have a post for beginners here to get you started! 

The first key to sewing in elastic is to get your machine settings right. You will use a stretch needle and a medium stretch stitch. Options for this are: a zig zag, lightning stitch, mock serge, triple stitch or a serger. Start by preparing the pieces for the bottom, front and back, self fabric and lining. Once you have the pieces cut out and attached at the crotch and side seams, cut your swim elastic to the lengths indicated in the pattern booklet.


prepared Faye bathing suit bottoms

Mark 1/2" from one end of the waistband elastic and overlap so that the other edge of the elastic meets the mark, ensuring it's not twisted. Sew together so elastic forms a ring. Divide the ring into fourths and use a marking tool to note each quarter. 

Insert the lining bottom into the swimsuit bottom, right sides together and pin together at top edge, dividing the waist opening into quarters.

Pin the waistband elastic to the waistband, matching marks aligning the top edge of all three layers.

inserting swim elastic into waistband

Starting at the side seam, sew down the center of the elastic to attach all the layers. 

inserting swim elastic into waistband

Understitch the elastic to the lining. Turn right side out. Match up the seams and leg openings. Serge, mock serge or zigzag the edges of the swimsuit fabric and lining together using a 1/4" seam allowance. 


The method we use to install elastic on the leg openings is called the turned finish and begins the same way as the waist elastic. Mark 1/2" from one end on both pieces and sew into a ring, matching end to mark. Divide each ring into fourths and mark or pin directly to each leg opening at quarters.

inserting swim elastic into leg openings

Stitch all the way around each opening sewing close to the outer edge of the elastic, gently stretching the elastic to the length of the fabric.

inserting swim elastic into leg openings

Turn elastic towards the lining and topstitch in place sewing close to the inner edge of elastic.

inserting swim elastic into leg openings



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