Sewing with Swim Knit


Swimsuit season is my favorite! Not because I love strutting around in next to nothing but because I can’t stop sewing swimwear! I’m excited to be here on the Cali Blog sharing my tips and tricks for sewing with nylon/lycra swim knit and to let you know it’s not just for the swimming pool.


My first tip is an important one. ALWAYS choose good quality fabric! Whether you’re sewing your first swimsuit or you’re a seasoned pro, the quality of your fabric plays such a huge role in what your experience will be like. Thin, slippery fabric with poor recovery will leave even the most experienced seamstress frustrated and ready to throw in the towel. I’ve tried lots of different swim knits from Cali Fabrics and each one has been so great to work with. You’ll want something with four-way stretch and great recovery. Look for something a little heavier weight if you’re just starting out. There are loads of ‘midweight’ swim fabrics to choose from on the site. A little thicker fabric will be easier to work with. There will be less curling and it tends to be less slippery as well. Once you’ve got a couple of suits under your belt you can tackle anything!


I love that Cali Fabrics is constantly adding new fabrics and their swimwear section is no exception. I snatched up this gorgeous lemon print last year and even had to go back for more once it arrived since it was even better in person. With the ever-changing selection you’re bound to find something for you.

When picking up your main swimsuit fabric you will also need a few other things. You will most likely want to line your suit. I line all the suits I make, even my kids, for extra modesty and comfort too (if you sew them separately you can hide all those inside seams between the layers!). You can use a swim lining fabric or you can self line with the same or similar fabric as the outer. Keep in mind that if you spend lots of time at the beach regular swim knit is the better option because it keeps sand out of the layers. Swim lining tends to be a looser weave and can trap sand inside the suit.

I like to add a layer of power mesh in my suits. Power mesh adds more stability where you need it. I added it to this suit in the front from the hip to the underbust using my pattern piece as a guide. I love the extra support it gives.


You will also need swimwear elastic. Look for something specifically made for swimwear sewing. Cotton swimwear elastic will hold up best to chlorine and the elements.

Thread is another thing to consider. Polyester thread will hold up best. I sew most suits on my serger and like to use wooly nylon thread in my loopers. It’s strong and stretchy and works great for swim and athletic wear. My new favorite thread to use in my regular machine when sewing knits and other stretchy fabric is Eloflex thread from Coats. You can use it in both your needle and bobbin but I’ve found that using it only in my bobbin has worked the best. I use a double needle on my machine to hem my swimwear and using Eloflex in the bobbin has been a game changer. My hems are strong and stretchy! Tip: Make sure your Eloflex thread doesn’t stretch too much as you wind it on the bobbin. I like to leave a little tail of bobbin thread before I begin a seam or hem and stretch my hem right after sewing it to make sure the bobbin thread hasn’t stretched too much while sewing thus ending up shorter than the top thread (and unraveling before my eyes!).


Ready to dig in?! First cutting swimwear can be tricky. I highly recommend using a rotary cutter, cutting mat, and pattern weights. Slippery fabrics are just so much easier to cut in a single layer without all the pins and the worry that lifting the fabric with your scissors brings. Now is the perfect time to grab that big box store 40% off coupon and pick up a cutting mat if you don’t have one yet. You will thank me later!

When sewing your swimwear you can use either a regular machine or a serger. On a regular machine I like to use a thin lightening bolt stitch for seams and a wide zig zag stitch for attaching elastic and finishing. You want your stitches to stretch so play around with your machine and find your favorite settings. Most of my favorite swim patterns have a wider seam allowance which helps keep the fabric from being sucked into the thread plate which is always my biggest concern when sewing thin fabrics on a regular machine. Clips are a lifesaver when sewing swim as well. Pins can leave holes or snag your fabric so clips are a great option. The more clips you use the happier you’ll be when you hit your machine.  Be careful as you sew that you are not stretching your fabric!

One of my favorite tricks I discovered when sewing this lemon suit was an easy way to turn those skinny straps. On my serger I made a tail a bit longer than my strap. Lay the tail through the middle of your strap lengthwise, keeping it attached to the machine. Sew your strap being careful not to catch the tail in the seam. When you’re done, gently pull the tail pushing the end to the inside and just like that your strap is right side out!


I also like to use my favorite slim fitting patterns for swimsuits.  For this suit I used the Layer Me Up t-shirt pattern from Patterns for Pirates and modified it to have a shelf bra and side ruching.  (Isn’t this floral fabric a dream?!)  I love rash guard type tops for a little extra coverage and this one worked perfect!  I also love to use raglan patterns for me and my kids for rash guards.  I don’t size down because you still want the shoulders and armscye to fit like a tee but will usually slim the sides just a touch depending on the pattern.  To add a shelf bra and cups to a women’s top, you will first need a lining.  I’m real technical and just hold up the lining to me and pin the cups in place, adjusting and straightening a bit after.  A shelf bra is essentially a strip of elastic just under your bust.  Cut a piece of 3/4″- 1″ elastic 2″ shorter than where you will place it on your lining.  You want to sew it just outside your side seam allowance or you will experience pulling on the outside of your suit, stretching it as you sew it in place.

I like to use leggings patterns as boy shorts swim bottoms, too.  Add elastic to the bottom hems to keep the legs nice and close to the body.  Just measure the leg opening and cut it the same length since leggings usually have negative ease built-in.


Not ready to sew your own suit yet? How about whipping up the perfect workout leggings in a cute print instead! Sewing your own athletic wear can be an easy way to dip your toes into working with nylon or polyester/lycra blends. Leggings are the perfect beginner pattern. There are only a couple of seams and you can use a yoga waistband, eliminating elastic as well. As you gain more confidence, you can move on to sports bras and tanks too. My little dancer loves her donut leggings!


My little guy is always falling in love with cool swim knit prints like this one. I love the new Euro style swim shorts for boys and men. They sew up quick and are so cute on! Being able to use my favorite swim fabrics for my boys is a win-win!

Thanks for letting me share my swimsuit obsession with y’all today!  You can hop over to my blog to see all the suits I’ve made in the past.  There’s tons of inspiration and loads of pattern recommendations too!  I hope you all can’t wait to ‘dive’ into to sewing with swim knits!

Patterns used for this post: The FREE Bonny leggings from Made for Mermaids

Mama Camila Swimsuit from Made for Mermaids

Palm Euro Swimsuit from Sew Like My Mom

Layer Me Up Shirt and Hello Sailor Bottoms from Patterns for Pirates

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3 thoughts on “Sewing with Swim Knit”

  1. Oh my gosh! Thanks for sharing this! I love what you have made, especially the tops in the lemon print. Your kids must be over the moon with their clothes!

  2. Thanks so much for this! I’d like to try sewing a swimsuit. Just to clarify, if I’m using my serger then what type of thread do I use in each of the 4 thread positions?

    1. Hi Erika, I use regular polyester serger thread in all but the upper looper. For the upper looper I use stretch nylon thread.

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