How to Insert Bra Cups into a Swimsuit


Adding cups to a swimsuit pattern is actually an easy modification that can make your suit instantly more supportive and comfortable. It’s pretty easy to slip swimsuit or bra cups into a suit or with a bit more work you can even add a cup with an underwire!

25 nautilus swimsuit construction

Choosing cups: There are many kinds of different bra cups out the biggest consideration you need to make is whether it’s the type of cup that is comfortable to you. You can buy softer cups that don’t give a lot of support but do provide a bit of modesty. Foam cups are a great choice for both support and modesty. If your foam cups aren’t specifically labeled for swimsuits, make sure that they don’t retain a lot of water like a sponge when they are wet! I find one of the best ways to source cups is to go to a thrift store and buy a very lightly used swimsuit and cut out the existing cups.

Sizing cups: Choosing a swimsuit cup size is much less exacting than picking a bra size so generally you will find them in a multiple cup size range (e.g. A/B or C/D). You can generally go by your bra size for size selection although my personal experience has shown that the cup will stay in place better and provide more comfort and coverage in your suit if you choose a cup that is a bit too big instead of a bit too small. For foam cups, you can easily trim them down to fit if you buy ones that are too big, although you can’t go down more than a cup size or two because of the shape of the underlying curve of the cup.


Inserting cups: Inserting bra cups into a swimsuit is as simple as sliding them in between the fashion fabric and lining. Make sure you do this during construction before you have enclosed all the side of the cup! If you forget or find that your suit needs cups after you are done, you can cut a slit in the lining along the side and slip in a cup after the fact. Depending on your cup, bust, suit, use, and fit, you may find that the cups stay in place without a problem or you may find that they slide around a bit. If they tend to slide out of place, try on the suit and pin the cups in place. Make a couple of tacks through the lining into the cup to keep them permanently situated in the correct location.

Lightweight alternative: If you don’t need much extra support and are just looking for a bit of modesty for when it gets chilly, you don’t need to insert a cup. Instead, cut out several layers of lining fabric and sew them as one for the cup lining. Multiple layers of fabric is typically preferred by smaller and/or perkier busted folks as it doesn’t do much for support.

insert underwire bra into swimsuit lining

Inserting an Underwire Bra Cup: If you have a well fitting bra (foam cup, with or without underwire) that you are will to sacrifice, you can easily insert it into your swimsuit as well. Cut your bra in half through the center and cut off the straps. Cut an X in the cups of your swimsuit lining (the size of the X will vary with your bust size), push the bra cups up into the X, and pin them in place.

underwire bra sewn into swimsuit

Sew the lining to the cups, being careful not to hit your underwire and use the lining piece in your swimsuit construction. You can machine sew through the cup itself or hand sew around the edge of cup.

underwire bra in swimsuit

To prevent visible lines from the front, you may want to cut away the excess lining fabric. If you want a pretty interior finish, you can cut a second piece of lining and use it on the inside of the sewn-in cups.

*Thanks so much to Elaine for the idea and photos of inserting a bra into her swimsuit. Read her mini-tutorial on Curvy Sewing Collective for more.*


Comments 21

  1. Awesome ideas. I was searching for “how to change the cup size in a swimsuit.” and got you. Very adorable profile pic.

    So I bought a swimsuit and the cups are for a DD or something and I’m about a C — pear shaped size 18, course all the 18 suits on Amazon prime for under $30 have huge cup sizes with underwire and a foam padding. I think I’m going to start with the foam, then the wire or vice versa. The wiring also makes the top unbalanced. So I’d rather altar my suit, then buy a new one and have to return it again and again and again. And I <3 the color and pattern.

    Anyway, thanks for the tips. Mucho appreciated.

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      Thanks! So glad that you found the information helpful. Best of luck with your alteration! Feel free to email if you have any questions while you work on the alteration.

  2. Hi Erin, I am about to embark on a big swimsuit sewing project and am really enjoying your tutorials. I previously added foam cups to my Soma one piece by sewing them into the lining. However I found that when the suit was wet they (along with the zigzag stitching) showed right through the suit. My fabric was a light color and may have been thin, causing this problem. Just wondering if you would recommend always using an extra layer of lining between the cup and the outer swimsuit fabric.

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      I’ve found that lighter colored swimwear is more likely to show through all sorts of things – from seams to cups to linings to parts of your anatomy you’d rather not show through! I’d recommend an extra layer of lining (or two) when using particularly light colored fabric.

      So glad you’ve found the tutorials helpful!

  3. Great tips! I am a 32DD and am in love with the one piece swimsuit trend this year… But there is no support! I think I’m going to buy one, sew in an extra piece of fabric to attach the cups into? I need to look perky and supported for spring break this year!

    Thanks for the tips

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    2. Hi Kelsey – just wondering if this worked? I bought a cute/ cheaper once piece and it needs to have some support added. Was wondering if it was worth the effort? If so, what did you do? Thanks!

  4. Hello, Thanks for all the info. I have a question about a tankini that has no elastic or mesh below the bust, just cups which do not support enough. I like to actually swim and this seems to just be made for sunbathing. I am hoping to add a mesh lining with elastic sewn to the lower edge, but am worried about how to do so with all the finishing done. Should I hem the mesh and just try to sew to the top back suit hem, under the cups and down the seams or should I open everything up and reclose with the mesh in place?

    1. Post

      How you choose to insert a mesh lining with depend upon how much work you are willing to do and how much you mind some extra stitching being visible from the outside. Frankly, I think ripping stitches out of a sewn swimsuit is a nightmare, so I wouldn’t do that. Instead, I would cut take a piece of mesh and hem it with elastic. Try on the suit and tuck the elastic-hemmed mesh into the inside. Pin it in place along the top edge of the front of your swimsuit, the underarms on the front of the suit, and then down the side seam. Topstitch the mesh in place where you have pinned (it’s okay to leave a gap across the straps) and then trim off the excess mesh. It won’t be lovely on the inside, but the stitches won’t be too visible on the outside (since you can stitch over the original topstitching lines). Again, there are many ways to do it, so do what makes sense to you!

  5. Can I just remove the cups and shelf bra from my suit without damaging the suit. I wear a separate swim bra under the suit and the shelf bra and sewn in cups make it too bulky. I don’t need any extra boob size!!

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      You should be able to do so. I would assume that they are stitched to a lining that is attached to the suit at the edges? I would recommend against trying to rip open any seams and re-sew them. Instead, you can just cut out the part of the lining that contains the cups since the lining itself shouldn’t unravel.

  6. I there! I’m a 32DD and recently bought a swim suit online which already has underwire cups in it. I’d like to remove them and insert new ones that are my size. However, I’m trying to find some sort of cup inserts online with underwire but I’m just finding generic “one-size-fits-all” padded lining without any underwire. Is there somewhere you recommend finding/buying them or will I just need to sacrifice a regular bra?


    1. Post

      I’m sorry, but I don’t have any specific suggestions. My recommendation would be to sacrifice a regular bra that you know fits you well- however you should be able to use a bra that wearing out as it tends to be the elastic on the band and straps that stretches out to wear out a bra long before the cups themselves wear out.

  7. Can you email me directly, so I may ask you a question about a swim suite?

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  8. What would you recommend I use for a shelf bra with cups..where the cup size of D-DD is not large enough? I’m making a tankini and frustrated with finding larger cups. Would multiple layers of lining work? I’m a lap swimmer. Is there a pattern available to make bra cups?
    Thank you for suggestions.

    1. Post

      Multiple layers of lining will give you some support, though it is a matter of personal preference if it is “enough.” Do you have an old bra where the cups fit but perhaps the back is stretched or the straps are uncomfortable? You can cut the cups out of your old bra and insert them.
      I would presume that you could use a bra sewing pattern to sew cups and insert them into your suit, although I’m not familiar enough with bra patterns to make a specific recommendation.

  9. I just purchased a one piece swimsuit that I love but unfortunately it is so revealing when wet. I am looking to insert some form of padding into the top so that its not so thin. I am small chested so I am not really looking for the support so much as the modesty. I am not sure where I should start!

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      If you’re not looking for additional support, you could just sew in an extra layer of swimsuit lining across top front of your swimsuit. That’s probably the quickest and easiest approach.

  10. Hello there,

    Love your How-To tips, I did that to my bikini top that didn’t have padding in it….and it becomes kinda revealing even it’s black :/ I have a question though. After I cut a slit at the side of the lining & insert a foam padding, I’m not sure what to do with the slit-opening. I’m a little worried it might cut wide open after wearing them for a while. How do I enhance the opening? Thanks:))

    1. Post

      Generally, I just leave the slit alone. Swimsuit lining shouldn’t unravel. If you are worried or yours shows signs of stretching you can sew it back together by hand. A catch stitch would be an easy way to do so.

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