Top 10 Tips for Sewing Swimwear

HelenSandpiper Swimsuit, Sewing Tutorials25 Comments

Top 10 Tips for Sewing Swimwear

Ready to dip your toes into sewing swimwear? It’s no secret that I love making swimsuits, but I know it can be an intimidating project for beginners who are new to sewing high stretch fabrics. The good news is that sewing a swimsuit is easier than you think, and it can be SO rewarding to finally make yourself that dream one piece or bikini. Plus, it’s super fun! All you need to be successful making your own swimsuit are the right supplies, techniques, and a little patience. Today I thought I’d share my favorite tips for doing just that!

Top 10 Tips for Sewing Swimwear

1. Purchase the right fabric. 

This is one situation where we want to avoid sewing with natural fibers like cotton or linen, which are very absorbent and will get too waterlogged for swimming. The gold standard for swimsuit fabric is a nylon and spandex blend (also known as lycra) with 4-way stretch and a spandex content of no less than 10%. You want to make sure it has lots of stretch and great recovery! Polyester knits can work too for swimsuits, just keep in mind that they might not hold up as well to the sun, chlorine, and saltwater. 

You can check out our full fabric recommendation list for the Sandpiper swimsuit here.

2. Choose a lining that works for you.

Lining fabric is an important component of swimsuits—it’s the fabric that sits directly against your skin and provides added support and stability to the swimsuit. In RTW suits you’re likely to see 100% nylon lining (sometimes referred to as Helenca lining), but in a pinch, you can also self-line with your swimsuit fabric. Some patterns might even call for this depending on the design or specific needs of the suit. Either way, this method tends to add bulk and might make your bathing suit feel tighter (so don’t be afraid to size up if you need to).

The other option (and my personal favorite) is using power mesh to line your swimsuit. Power mesh is commonly used in lingerie or activewear to provide an added level of strength and support to garments, making it a great option if you want to feel a little more secure in your suit. Power mesh tends to have a lower stretch percentage than regular swim fabric, so like a self-lining, you may need to size up.

Sandpiper Swimsuit Closeups

3. Use swim-specific elastic.

All swimsuits require elastic, but you want to avoid using standard polyester elastic because it will not hold up to chlorine and salt. Instead, look for chlorine-resistant cotton or rubber elastic. Make sure it’s labeled specifically for swimwear! If you simply cannot find swimwear elastic, you can sub regular elastic in a pinch. Just be aware that it may deteriorate faster.

4. Check your measurements and the size chart.

Swimsuits are harder to toile (you can’t use a cotton muslin, after all), and the negative ease might have you scratching your head when the finished measurement chart is smaller than your own measurements. Don’t worry—this is correct! Swimsuits are designed to stretch over your body so they fit snuggly and you don’t have any wardrobe mishaps. 

For the most part, knits are pretty forgiving so you don’t need to worry much about doing all of the same adjustments you would for a woven garment. That said, there are a couple of things to keep in mind. Pay particular attention to the height your pattern is drafted for, and adjust the lengthen/shorten lines accordingly. If your bust is within 1-3 inches of the pattern draft, you probably don’t need to worry about an SBA or FBA. Any more than that and you might want to consider doing a Full Bust Adjustment (FBA) or adding length in the bust and width at the front side seams to increase the room for the bust.

Swimsuit fit is SO personal! Some people may want a looser fit and others may desire a compression suit. We have added a page to the Sandpiper Swimsuit instructions where you try on the main swimsuit pattern pieces and assess the fit. This is a great opportunity to take the swimsuit in and make it tighter where you feel it is needed.

Sandpiper PDF Size Chart on a Tablet

5. Cut your pieces accurately.

Swim fabrics can be pretty slippery, but luckily there are a few things you can do to make cutting less difficult. First, try to cut your pieces on a single layer—this will not only be easier, but you’ll also get more accurate results. This is a great time to bust out the rotary cutter and pattern weights. Make sure to cut with the printed side of the fabric facing up, so you can be precise about pattern placement and avoid a misplaced flower or design feature. 

It’s also especially important to pay attention to the grainline when you’re cutting your pieces. Because swimsuits are so stretchy, pattern designers carefully layout the pieces in such a way that the intended stretch direction matches the needs of the swimsuit design. This will either be along the grainline (parallel to the selvedge), or the DOGS, aka direction of greatest stretch (often but not always perpendicular to the grainline). Either way, take note of how the pattern wants you to cut the pieces and make sure you are doing so accordingly. 

6. Make sure you have the right needle, thread, and pins.

This one is huge since high-spandex fabric can be especially fickle about needles—and we all know how frustrating skipped stitches can be. Make sure you are using a stretch needle that is suitable for the weight of your fabric (you might need to test to find exactly the right size). Some people have luck with ballpoint needles (also called jersey needles), but I’ve personally had more success with stretch needles, and that is what is recommended by most needle manufacturers for high spandex fabrics. I have also found Microtex needles to be great for sewing elastic. They are super fine point needles that can go through the elastic without bouncing. When you’re pinning, use ballpoint pins to prevent holes or snags in the fabric.

Sewing Swimsuits, Correct Needle Type Examples
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For thread, you want to stick with polyester which will hold up best to chlorine and salt. Try to use a name brand if you can—lower quality thread can cause skipped stitches, even when you are using the correct needle. If you’re feeling adventurous, you can also try using woolly nylon thread in the upper and lower loopers of your serger or in the bobbin case of your regular machine. This is a great way to provide extra stretch to your swimsuit without sacrificing strength—but it’s totally optional! A serger or overlocker is not necessary to sew swimwear, but it can be used in conjunction with a sewing machine for certain finishes.

7. Use stretch stitches.

This might go without saying, but stretch fabric = stretch stitches! Sergers are a popular choice for the inside seams of swimsuits, but there is no reason you can’t use a regular machine to sew the entire swimsuit. The zigzag stitch, triple zigzag stitch, and lightning bolt stitch are all fantastic options. The pattern instructions might recommend specific stitch settings, but you should still test since your individual machine and fabric choices will add some variability. You’ll want to check that you can stretch your test swatch without any popped stitches to ensure your finished swimsuit will hold up to normal wear and tear.

Keep in mind that swimsuit fabric doesn’t fray, so raw edges are okay! It can be really fun to hack your swimsuit pattern with a cute peplum or ruffle detail and not worry about finishing the hem.

8. Don’t pull the fabric while you sew.

You want stretch fabrics to have some give when you wear them, so try not to stretch or pull the fabric taut as you sew. This will distort the final shape of the swimsuit and you’ll lose some of its stretchiness. When you are attaching binding pieces or elastic to your suit (which are smaller than the main fabric pieces), you’ll need to stretch those just enough so that they are the same length as the main fabric, but not any further. 

Sandpiper Swimsuit by Helen's Closet Patterns

9. Skip the iron.

I’ve never had much luck ironing lycra fabrics, and have found that finger pressing works just as well. In fact, synthetic fabrics can melt with too much heat, so if you do decide to iron make sure to keep the heat setting really low. If you have a seam that you want to make sure has a crisp, flat edge, you can try topstitching it down with a zigzag or triple zigzag stitch instead.

10. Rinse your suit after swimming.

You’ve spent time and money making the perfect swimsuit, you want it to last right? Even with all the appropriate fabric and materials, chlorine, salt, and sun exposure can all take their toll and can affect the lifespan of your garment. Make it a habit after swim days to rinse out the pool or ocean water from your swimsuit before it dries (either during a shower or by soaking it in a bowl of cold water for 30 minutes). This will help keep your new swimsuit looking great for years to come.

With these tips in hand, you are well on your way to making the swimsuit of your dreams! Do you have any other tricks for sewing swimwear? Let us know in the comments!

Grab the new Sandpiper Swimsuit for 20% Off this Week

Don’t forget that the Sandpiper Swimsuit is on sale for 20% off until July 22, no coupon code required!

About the author


Helen Wilkinson is the designer and founder of Helen's Closet Patterns. She also co-hosts the Love to Sew Podcast! Helen is obsessed with all things sewing and strives to share her passion and knowledge with the sewing community.

25 Comments on “Top 10 Tips for Sewing Swimwear”

  1. Thanks for this post! I plan to be in the water a lot this year and I’m going to need many bathing suits that I don’t want to “buy”. I’m going to get started on playing with some custom pieces!

  2. I’m now in the process of taking off the elastic on one of my favourite bathing suit that lost it’s stretch. The elastic is stuck on the fabric in places and a lot of stitching to remove. In your opinion, is it worth all the work involved?

    1. Hi Angela,

      That is a tough one. I would personally say no, but It is possible to do it, so it may be worth it for you. I rarely un-pick knits, I just move on to new projects!

  3. I started the summer with 4 decent purchased bathing suits. Three of them now have stretched out elastic only in places around the back of the leg. Can I remove just the problem part of the elastic and replace it? I’m afraid I’ll wind up with a thong if the elastic is stuck and I have to cut fabric away.

    1. Hi Ann,

      That is a bummer! You can try to unpick the swimsuit and remove the elastic but it may be challenging. Unpicking stitches on knits, and particularly swim fabrics, is not very much fun. It is do-able!

  4. I’m just making my first swimsuit which is going OK except my overlocker doesn’t like the fabric that much; the fabric either bunches under the cutting knife and doesn’t come away cleanly or the fabric doesn’t run smoothly through the machine so the stitches are bunched into a clump – like the dog feed isn’t working. So one way or another, lots of ‘clumpy’ stitches. Any suggestions welcomed

    1. Hi Tonia! This sounds frustrating! I usually don’t bother with my overlocker on swimwear – I just use my regular machine. Since the suit is lined, it all gets hidden away in the end. That being said, you can try putting ballpoint needles in your serger, and it might be time for a new blade, too!

  5. Loved this blog, but i have a question about a good fabric to try to make a toile? I want to make sure my fit is good, before i cut into my nice blackbird swimsuit fabric!

    1. Hi Ann! It is hard to make a swimsuit Muslin out of anything other than more swimsuit fabric. You can try to get some cheaper lycra to check the fit, but even then it might not perform the exact same as your final fabric. I like to over-buy swim fabrics so I can make two suits when Im using a new-to-me pattern. If that is not an option, a jersey knit with similar stretch can be an option. In the case with Sandpiper, you can also cut and sew the shoulders, side seams, crotch, and then try it on to make any minor adjustments before attaching the elastic.

  6. What tips do you have for sewing with rubber elastic? I tried to join the ends together and the holes made the elastic unusable as it just ripped. I used a stretch needle.

  7. Hi Helen, I only have a straight stitch machine that was gifted to me and I tried hand sewing a swimsuit top which I don’t want to do again! I also want to make some clothing in addition to swimwear. Would you recommend I purchase a regular sewing machine that has a zigzag stitch or a serger? Thank you for your advice.

    1. Hi Marianne,

      I personally think a new sewing machine that includes a zig-zag stitch and buttonhole function will be more versatile than a serger.

  8. Hi Helen! Where I live, I only swim in lake or river water and occasionally the ocean. In these circumstances, do you think it’s fairly safe to use regular elastic rather than swimwear-specific elastic? Thanks!

    1. Hi Alex,

      Yes! I think it is fine. Chlorine really is what does in the elastic. That said, salt water can also degrade elastic and spandex. Make sure to rinse your suit. No elastic or spandex lasts forever, so regular elastic will probably be just fine for lake/river swimming.

    1. We got them from Blackbird Fabrics and Discovery Fabrics. Blackbird usually does a swimwear line in the late Spring, so keep your eyes out for that!

  9. Do you sew your seams with a zigzag stitch, and if so, what length and width do you suggest? Same question for topstitching

    1. I like to construct my seams using the ‘lightning bolt’ stitch because it is nice and stretchy, but it is not wide like a zig-zag. If this is not an option, I would suggest doing some tests and figuring out what width is stretchy enough for you without breaking when stretched. For topstitching, it is also personal to what you like the look of. I personally like about a 4-5 mm wide topstitch.

  10. I have a question about the Tank ( or tankini) top. No one has mention how to deal with semi-bra support. Can you just use an elastic or swim fabric band in the front only? And just add the stretch mesh to cover breasts? This is what I want to attempt, but no idea if it will work or not? All the “ Tankini” tops I found online and elsewhere were either too darned tight, too loose, or far too short! Seems like there should be a way to do this!

    1. Hi Connie,

      Adding powermesh as a lining is a great way to add support. You can also add removable foam cups or sewn-in foam cups. I think it depends on the tank you are using and what level of support you are looking for. You may need to try making a few to find the perfect balance!

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