The Ins and Outs of Sewing Swimsuits

JUL 2, 2019 updated May 20, 2021

Are you ready to have some fun in the sun? Katie Kortman, the designer, sewist and painter behind all those colorful fabric designs taking over your Instagram feed, is stopping by the blog to tackle one of summer’s most popular DIY projects: handmade swimsuits! With her top tips, you’ll have the confidence to sew a swimsuit using Spoonflower’s Sport Lycra, her go-to fabric for swimsuits. For an added bonus, we’re offering 15% off Sport Lycra for the entire month of July! Read the post to find out how you can save on your next swimsuit.

Katie: It’s July. It’s hot. You just want to stay inside but if you must go out, there needs to be water, am I right? If you like to sew, you may have thought about sewing your own super cute, totally flattering swimsuit in a fabric more exciting than what is offered at the store. But you’re scared. I have heard people tell me this time after time. I get it. Until last summer, I was the same way. I could sew pants, dresses, shirts… anything! But a swimsuit? No, I must not be skilled enough for that. Or the dreaded thought… what if something malfunctions when I get into the water?

I am here to tell you that all those fears are for nothing!! If you can follow a pattern and know how to sew a zig-zag or straight stitch, then you can sew a swimsuit! 

Already a pro at sewing swimsuits?
Check out this post to see which swimsuit patterns and fabric designs I’m loving this summer.

There are many types of swim fabrics to sew with, but today we are going to talk about Spoonflower’s Sport Lycra. This post has tips that you can apply to sewing anything with Sport Lycra, even athletic wear!

Featured Designs

Sport Lycra Specs

  • UVA blocking at 99.9% and UVB blocking at 99.6% with a UPF rating of 50+
  • Made of 88% polyester, 12% Lycra knit fabric
  • Stretchy, sturdy construction
  • Moisture-wicking finish
  • 4-way stretch, 75% in width and 50% in length
  • Colorfast to chlorinated and salt water

I found this fabric to be the easiest to sew of all the bathing suit fabrics I’ve worked with. It is actually easier than most cotton knits I’ve sewn because it is thick and not slippery as you sew (and swimsuits are more forgiving than say… the hem of a stretchy knit shirt). 

Pro tip: Did you know there are no minimums at Spoonflower? This means you can order just one yard of fabric to create a completely one-of-a-kind swimsuit! 

Today I’m going to give you tips for sewing swimsuits with Spoonflower’s Sport Lycra but for general tips on sewing with knits, be sure to check out this blog post! I have now sewn 13 swimsuits with the lycra and I can confidently say this fabric holds up to all the elements!

First, let’s talk tools.

Needle: You will want to use a ballpoint/ jersey/ stretch needle in your machine. 

Pins vs. clips: Both work, but I found clips quicker and preferred them because it meant less holes in the fabric.

Thread: Polyester – avoid cotton thread! I have used Eco-flex, wooly nylon (in the serger – and you just do the two loopers), Coats and Clark poly (all purpose) and finally Gutterman Poly. I prefer Gutterman thread in my sewing machine because I’ve had the least amount of breakage and skipped stitches when using that thread. I still do like the wooly nylon in my serger but its not totally necessary. 

Scissors vs Rotary Cutter: If you have the space, a mat and cutting table, use a rotary cutter on your lycra because it will ensure a more precise cut. You can also just use your sharpest scissors and cut on the floor. Work with what you’ve got!

Pattern weights: Again, you can pin the patterns, but the best way is to use pattern weights and rotary cutter to prevent piercing the fabric and to get a more precise cut. I did use the weights as opposed to the pins in these five swimsuits and I prefer them to pinning the pattern down. 

Swim Elastic: Swim elastic is made to withstand chlorine and salt water. You can get it online or in most big-box fabric stores. I ordered a huge roll of it so I didn’t keep running out. 

Don’t forget to line your swimsuits!

Because the Sport Lycra is thick and opaque, many prints won’t need any lining, especially if it’s for a child’s swimsuit. I chose to line all of these suits since they were for adults. You will want a nude, white or black swim lining (two fabrics on the left) depending on the designs you’ve chosen on Spoonflower. 

You can also get something called Power Mesh which is found near the swim fabrics at big-box stores and online (two fabrics on the right). It is used to hold in the bust and/or tummy and can be sewn to the lining so it acts as one piece of fabric. Many patterns will mention its use in the instructions.

Pro tip: Spoonflower’s Sport Lycra also works great for lining your swimsuit. For an added bonus, choose a coordinating print from your main swimsuit fabric.

Now let’s talk about the stitches.

You want your swimsuit to be able to move and stretch so you can do big jumps and cannonballs right? Read on to learn how to ensure those stitches don’t pop! 

When sewing swimwear you are working with negative ease which means the pattern is written slightly smaller than your measurements so that it can be tight and stretch to fit your body. Because of that, you need to use stitches that can stretch and not break. The photo below shows four stitches/methods you can use to sew your swimsuit.

From top to bottom: Lightning/Stretch Stitch, Regular Zig-Zag, 3 Stitch Zig-Zag and Straight Stitch

Straight Stitch

With normal knits you wouldn’t want to use a straight stitch because you don’t want to stretch the fabric as you sew, but with swimsuits you can! If you stretch the fabric behind and in front of the presser foot AS YOU SEW, you can use a straight stitch! (It works believe me! But you HAVE to stretch the fabric as you’re sewing it or it will just break when you put it on.)

3 Stitch Zig-Zag

This is a zig zag that uses three little stitches on each “leg” which makes it an extra strong stitch that can also stretch!

Regular Zig-Zag

Most swimsuit patterns just tell you to do a zig-zag for all stitching which works fine. You can adjust the length and width of the stitch to get the look you want.

Lightning/Stretch Stitch

This is like a tiny zig-zag. Not all machines have it, but it works great if yours does!

Ready to talk about swimsuit construction?

Many parts of the construction can be easily and quickly done on the serger, but you will still need to use your sewing machine for finishings. You can do any of the steps with just a zig-zag or other stretch stitch if you don’t own a serger.

When cutting out your swimsuit pieces, pay attention to where the pattern lies on the body, and how it looks next to the other pattern pieces when you are using prints that are not a basic repeat design.

The photo above shows a method of elastic insertion that I hadn’t seen in other patterns. You simply put the elastic ⅛” in from the edge of the serger so it cuts off the excess fabric but the serging stitches encase the elastic as it sews! Most patterns just have you zig-zag the elastic to the seam allowance and cut off the extra ⅛” which also works great.

Now that you know the ins and outs of sewing your own swimsuit, find out how to choose the right fabric design and swimsuit pattern!

Save 15% on Spoonflower’s Sport Lycra now through July 31, 2019 with code DIYSWIM719.


About the Guest Author

Katie Kortman is a sewist, artist, and self-proclaimed dancing queen. Over the years she has sold her artwork in galleries, worked as a display artist for Anthropologie, taught high school art, had a handmade accessories company called Blue-Eyed Freckle, and mothered her four children. She has lived in many places around the globe as the wife of a Navy Doctor, but currently resides in Virginia.  

Katie enjoys combining her passions into one by using her artwork to design fabric on Spoonflower, that she can then sew up into clothing (and DANCE). She blogs at katiekortman.com and over on Instagram you can find her @katiekortmanart where she dances around in her handmade wardrobe.



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  • Donna Pierce

    I love this idea! opens up so much potential to now diy Aussie cover all swim wear from being mostly black. We have full body suits with plastic wide teeth zipper tops over tights (for foreigners at water parks in 35*celcius average summer temps.) . Most children also wear lycra swim t shirts! Now I’m thinking……😄

  • I am excited to try this, although I still find it a bit daunting. Any thoughts on what fabric would work best for a boy’s swim short? I usually only work with some of the cottons and eco canvas types because I make bags/hone decor. Thanks! Darcie (dnbmama) on Spoonflower

    • Hi Darcie,
      You can do it! Sport Lycra is a great option for both adult and children swimwear.