Swimsuit Sew-Along: Altering for Style

This post is one part of a Swimsuit Sew-Along series! If you missed the previous posts and would like to join in, just click below!

If you would like to add bra cups, raise a neckline or add/change straps, then this post is for you. I will cover some of the most common style changes I have encountered and will set you up with some great tutorial links for all the how to’s.

Adding bra cupsSometimes you find a great suit style but really want some inner support. And by all means! We’re making a suit so you want to take advantage of the opportunity to make it what you want! The best tutorial I’ve seen for this is not a swimsuit tutorial, but it works exactly the same. This Tutorial: How to sew a built-in bra (with cups!) has been cruising around pinterest for a while and it’s applicable to us because she makes a t-shirt with a built in bra sewn into a lining layer. This is exactly how a swimsuit is structured. Every women’s suit will have a lined front, even if only in the bust area, so you can just follow her tutorial for adding bra cups and presto-change-o you’ve got a great feature in your custom sewn swimsuit.

Altering leg hole/brief styleI had a question from one of our sew-along participants asking how to alter a brief bottom to be more of a boy-short style. After a little google research, I found this FREE pattern download & instructions at Cloth Habit. You could use this to alter a one piece suit too, by laying the boy-short pattern under some tissue paper. Line up your swimsuit pattern to match the crotch seam, for example (or however it lines up on your particular swimsuit pattern), tape the your swimsuit pattern to the tissue and draw the new leg hole. This pattern has a center seam, so to account for that in your suit (unless your swimsuit also has a center seam), draw the stitching line on the boy shorts pattern and line that up as best you can with the “cut on fold” line on your swimsuit pattern. This will ensure your boy short doesn’t turn out too wide.

neckline suitAdding neckline coverage: Another style alteration you might want to make involves gaining more coverage in the neckline. For a swimsuit with a halter neckline like the one pictured to the left, you could save scraps or buy a small piece of contrasting fabric to sew in place that would act as a camisole. After constructing your swimsuit, hem the top of the scrap (to be the top of your insert), try on your swimsuit and place it where desired between the straps/bust. Pin it in place and sew down the neckline on both sides using a straight stretch stitch, twin needle or a very narrow zig zag. Other styles with a scoop or v-neck can easily be drawn higher by starting at the shoulder seam, marking the height on the center front and mimicking the line of the original pattern down to the new neck height marking. Remember, you can always take away later, but it’s definitely more challenging (or near impossible depending on the situation) to add more.

Changing the Strap/Adding Straps:  After making a few halter neckline suits and a few strapless, I’ve come to realize I just feel more comfortable in a regular ol’ over the shoulder down the back strap. While criss-cross, halters using ties or bra hooks, and strapless can all be cute and flattering, I’m just not comfortable in the long run, so I’ve learned to stick with my tried & true. Adding straps to a halter is by far the easiest addition you can make. For my last swimsuit, I just took a long strip of my fabric, folded it in half right sides together and sewed all the way down. I used a turning tool to turn it inside out, attached them to the back of my suit where it seemed right and then tried it on, pinning the straps in front where I felt they worked best. Another way to make a strap is by encasing your elastic in this strip of fabric like this. This is probably what I should have done with mine, so if for some reason mine start to fail, I can always go back and do it right.

If however, you have a halter as shown above, you may have to do some legwork. Since this type of halter is designed and cut to wrap around your neck, the easiest fix is to cut the straps long and cross them in the back before sewing them in place on the back of your bodice.  Any halter with spaghetti straps, intended to be tied can be done the same way and even possibly made into the regular ol’ over the shoulder down the back strap. Just try it on and have someone pin your straps various ways to see what works best.

Did I miss your specific alteration? Let me know what you’re facing – I’d love to help you out! While some of these alterations are done before cutting/sewing, some won’t be finalized until we are in the process, so be sure to tuck this post away for safe keeping if you will need to alter as you sew. Now we are ready to cut out our swimsuit so grab your pins and a yardstick, ruler or quilting ruler and I’ll see you Friday!


48 thoughts on “Swimsuit Sew-Along: Altering for Style

  1. Pingback: Swimsuit Sew-Along: Cutting It Out | Jaime Johnson

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  4. I really need to take my one piece in a size up top. the bottom fits great but the top is too big. How would I alter that? What kind of thread/stitch should I use?

    • Hi Lisa – thanks for stopping by! Depending on the style, you can just take in the side seams starting at the top and gradually sew out to the original seam line at the waist (or wherever the fit starts to be right on you. You should use a stretch or ballpoint needle, polyester thread and a stretch straight stitch on your machine (it looks like a tiny zigzag) or just use a very narrow zigzag stitch. Hope that helps!

  5. I have a question about altering the crotch, Should I measure the width of someones crotch? I’m having issue that bottoms for my daughter have way too much fabric between her legs and it bunches up real bad, I’m afraid of taking too much out and her lady parts might show. I didn’t alter a bottom and on the beach this week sand got between her leg and the elastic and rubbed her raw. I was thinking if it fit better she wouldn’t have had this problem.

    • Hi Michelle! Thanks for stopping by! I would compare the suit to a pair of their underwear. You could line them up and cut the suit to their size (plus seam allowance) and it should fit much better.

  6. I have a one piece swimsuit that looks like a 2 piece tankini set. It has control fabric from the bodice to where the “bottoms” begin. I bought it so the top fits (sz 14), but I wear a sz 10 in the bottoms. I wore it in the pool last summer but the wet fabric was very clingy to my lady parts because of the excess fabric. I ended up purchasing shorts to wear over the suit in the pool. How can I alter the bottoms so they will fit?

    • Hi Laura, Thanks for stopping by! It would depend on where they were big. You could take in the side seams using a narrow zig zag stitch or serger if you have one, and just taper up to the seam allowance on the part of the suit that fits you. If you need to pull them up a little, it sounds like you could take a little on the waistline seam where the bottoms meet the control fabric. Without seeing it, I’d say you just will need to put it on and play with tucking out fabric in different spots until you get the fit you want. If you feel confident, you could remove the leg elastic for a cleaner alteration or just literally stitch up the side seam making sure the bottom matches up well. Wish I were right by you to give you better advice! Hope that helps some.

  7. I’d love to know how to alter a bottom on the swimsuit. I’m scared to touch it because of the fabric. It’s for a 7 year old. The bottoms are loose. The smaller size just was to tight. She’s got curves! The difference I need to take up I’d very small. So I’m thinking I’m going to have to rip out the seams in order to do both sides for the best look and fit. Do I need a specific thread, foot on my machine, needle, stitching, ect. I can’t see paying someone to fix them due to the cheap cost of the suit. I’m concerned about the needle putting large holes in the suit and the thread not staying put. We swim almost every day and I machine wash suits after each use. Air dry. Thanks!

  8. Hey there! I have a gorgeous one piece I recently found at a thrift shop for super cheap. The problem is that it is about one size too big for me. I saw your comment earlier about stitching inside the side seams, but would this work the same way for a ruched bathing suit?

  9. I’m “plus size” and am having problems with bathing suits. I prefer one piece but unfortunately, plus size suits all have great expectations in the top area. While the suits fit me, the foam/molded cups are just way too big for me and look kind of ridiculous on me. Any advice on making it fit on the top/removing and adding something else instead?

    • Hi Elle! Are you referring to altering a store-bought swimsuit? It would be hard to say without seeing the swimsuit/style, but if you’re comfortable with sewing knits, you could cut out the cups or the whole bust lining and purchase cups that fit to make your own lining. This tutorial mentioned in the post: http://daughterfish.com/?p=3228 is good for guidance. If the top of the suit is overall too lose, you would just take it in as much as needed and taper out to the waist (or where ever it fits correctly). Hope that helps!

  10. Hi! I recently ordered some swimsuits from a shopping app, so I didn’t get the opportunity to try them on before buying them. They fit me wonderfully everywhere except for the top and I absolutely LOVE them. I really don’t want to send them back. I am a D cup and although the swimsuits I ordered are larges, my boobs are spilling out all over the place. There is a little bit of padding in them and I’m not sure if removing the padding would help or not. They also have underwire in them, which I need because I can’t have swimsuits without support. Is there any way to alter these swimsuits to accommodate my larger chest?

    Thank you,

    • Hi! It sounds to me that there is just not enough fabric in the bust area to accommodate the bust size. Depending on the style, you could add fabric at the neckline, a faux camisole look? Removing the padding might help a smidge depending on how thick it is, but I understand needing support and the padding does add to the support. What is he style of the top?

  11. Hi! I ordered 2 of the same bikini bottoms in different colors off of a shopping app on my phone and they are a little on small side! I obviously need to alter in crotch and both side areas which I’m guessing entails the addition of fabric? I’m new to sewing meaning I’ve never sewn before😁 can you offer any suggestions or tips on how to achieve this alteration in my bikini bottoms? Thank you in advance for taking the time to reply and help me in my dilemma😊

    • Hi there. Assuming you want to alter the crotch with the ultimate goal of bringing up the rise, I wouldn’t mess with the crotch, I would add a contrast waistband. Ebay has a ton of swimsuit fabric for sale – I would search “nylon lycra” and make sure the listing mentions swim/dance and 4 way stretch. If you still need room in the side seams, you could just cut on each seam seam and add the amount of fabric you need, before adding your waistband. You may also consider just ebaying them as is to recoup your money and buy new bottoms! lol. It just depends on how much you like them and how much you want to fuss with the alterations. Hope that helps! Thanks for coming by and commenting!

  12. Hi. I have a swimsuit that I really like. It is just a regular shoulder strap swimsuit with a skirt. I will be having weight loss surgery in a few months to remove a lot of loose skin…I lost 180 pounds. I’m pretty comfortable in this swimsuit…it took a really long time to find one that covers all my problem areas. Would it be possible to change into a halter style? I would just like a different look this summer. Thank you for your time!

    • Hi there! Thanks for stopping by. Yes – it would be super easy to turn a strapped suit into a halter. Without seeing it, I imagine you could just cut the straps close to where they’re attached in the back and tie them as a halter instead. You might want to make a small knot at the end of each strap or turn under 1/4″ of the raw edge to the inside and stitch by hand or machine just to finish off the ends. Also, if the strap is wider than a spaghetti strap, it might buckle strangely where it’s attached due to the strap changing direction (from straight back to diagonally around your neck). If that bothers you, you could detach the strap at the front and re-position it slightly diagonally to the top edge so the strap lays nicely. Hope that is helpful!

  13. I bought a one piece online this season and I love it. The only problem I’m having is that I’m so long waisted that it doesn’t fit properly. Is there anyway to extend the length?

    • I am doing this exact alteration this year. I don’t know why the suits seem so short waisted!! I’m planning to cut the suit all the way around at the natural waistline and add a 1-1.5″ piece of swimsuit fabric in between the two halves. When sewn back together it will look like a belt or sash, a style I’ve seen on several sites this year. Please let me know if that needs some more clarification. Thanks for reading!

  14. Hi Jaime!

    I don’t know if you can help but i’ll ask you anyway 🙂 I bought this beautiful black and white swimsuit (http://www.venus.com/viewproduct.aspx?BRANCH=24~97~&ProductDisplayID=25694)
    The white foam cups on the lining are showing through when i wear the swimsuit and i have two big white round shape on my breasts, and that’s all you can see! (the picture on the website has obviously been Photoshopped since they’re not showing) .

    I really don’t want to send it back and am wondering if there is a way to cut the cups from the lining and replace them with more of the same kind of lining, with a discreet seam that wouldn’t show when i wear the swimsuit. I wish i could attach a picture to show you the swimsuit….

    I am not really good at sewing this kind of elastic lining so any advice would be great. And i think I’d have to do it by hand as I don’t want to undo the side seam in order to use my sewing machine to fix it.

    if I can send you a picture, i’d be happy to.

    Thank you so much for any help you can provide.


    • Beatrice, Thanks for stopping by! A good thing about that knit lining is that it will not fray when you cut it. You could certainly cut out the cups and add lining. Since it won’t fray, there’s not need for a seam, you can literally lay the lining on top of the new piece, pin it in place and then stitch with a zig zag where you took out the cups. Once you’ve secured the new lining in place by stitching around the missing cups, you can cut away the excess new lining. If you’d like to send more pictures, please feel free to email me at madebyjaime at gmail dot com.

  15. Quick question. I recently bought a new bikini online, so I was not able to try it on. The bottoms don’t fit right at all, the crotch section is like 5 inches wide so it just bunches up and does weird things. Is there any way to take in the crotch section so it isn’t so wide?

    • Hi Brittni – Yes, I would just take a pair of underwear or another swimsuit that fits you and line it up with the too-big suit. Cut adding a 1/4″ – 3/8″ seam allowance to all edges (depending on the width of your elastic) and then sew new elastic to the leg holes. Hope that helps!

  16. Hi Jaime, my niece kindly bought me a beautiful suit with an overskirt that is heavily ruched all the way down the sides. It’s not attached to the suit itself, so it just slides down and looks dowdy. I’d like to gather the overskirt and tack it to the suit along the seams (on the top layer of the swimsuit and the seam allowance of the overskirt) to hold it in place so that it will maintain the gathers across the front and back of the swimsuit without me having to constantly mess with it. Can you think of a more effective way I could permanently attach the overskirt? Thank you for any advice!

    • Hi Mickey – thanks for stopping by! I think you have a great idea. If you’d like the rouching to maintain it’s adjustability, you could sew just the first few inches of the skirt at the waist, if I’m picturing the right style, and leave the bottom unattached. Hope that helps – feel free to reply with any follow-up question!

  17. Hi Jaime- I have a swimsuit that I absolutely adore but I could really use your advice! It’s a one-piece with molded cups and thick halter straps. The cups fit great, but the suit is a little bit loose around the ribcage and I find myself having to lift “the girls” back into place every 10-15 minutes. The back of the suit comes up right about to where the bottom of the cups sit. I’m trying to figure out if there is a way to sew in ties or a strap of some kind on the back so that I could tighten the cups to my ribcage (sort of like a tie-back bikini top). I’d love some input- thanks so much!

    • Hi Amanda! You could add a tie back to the side seams just above the back of your suit, but I worry that the suit below it might gap. Is the front fully lined or is there some kind us elastic under the cups? If there is a half lining with elastic there, You could replace with a smaller piece it to tighten it under your bust. If it’s loose around the ribcage it might help to bring in the side seams there so the suit is more snug on you in general.

  18. good morning! I bought a bikini yesterday (top is a triangle bottom is a string with ruching on bottom) it has a beautiful lace overlay on the whole thing so it does not stretch one bit! The bottoms will not even cover my lady parts lol.. Is there anyway to add or incorporate extra fabric or combine two bottoms for more coverage? Thank you for any help

    • It might be easier to pull the lace off and sew a new bottom, then use the lace to embellish the new, correctly fitting bottom. Otherwise, as you mentioned, you could take a second bottom and basically cut the amount you need for coverage off each side and sew to the remaining bottom along the whole leg-hole, from string to string, if that makes sense. Would love to know how it comes out!

  19. Jaime, my 13 year old daughter found the “perfect” suit on line size large . When it arrived it was a 3XL! After ordering it again we had the same thing happen. Long discussion with customer service basically determined the third party vendor doesn’t seem to have a Large. She LOVES this cute retro high waisted suit and has found no others that she likes. I can handle the bottoms but the padded top is tricky. There is no underwire but a side “wire”. The padding was supposed to be removable but it seems to be sewn in. Do you think there is any way I can alter it?

    • If the padding is tacked in, I would remove the stitching to get them out so you can make the alterations you need. The side wire (boning) can be removed as well. If not, it’s hard for me to say without seeing it. If you send pictures of the suit to madebyjaime at gmail dot com I can maybe give you some tips! Thanks for stopping by!

  20. I have a one piece Speedo swimsuit with a very conservative bottom. Almost to the point of being boyshort like. Want to adjust so more of my leg shows. Guess I’m trying to do the opposite of your article section about making into boyshorts.

    • Hi Joseline – in that case you can just use a pair of underwear or another swim bottom to guide you on where to cut. I would line them up and cut at least 1/4″ away from the desired underwear line to allow for the elastic hem. Hope that helps!

  21. I have a one piece sarong suit with a half skirt that is too long for my short torso. How would I cut and finish the skirt area? I tried to zig zag the cut edge on an old suit and it flips up. Thank you for your attention to my problem.

    Judy from upstate NY.

    • Hi Judith! I would turn up even just 1/4″-3/8″ hem and zig zag from the wrong side or use a twin needle from the right side. Pressing the hem when you finish should help it hang correctly or if you want to add weight to the hem, you can use swimsuit elastic in the hem – just don’t stretch it as you sew it in. Hope that helps!

  22. Hi. I have a strapless tanking top that digs in on the sides under my armpits and hurts me. Any suggestions on what I can do?

  23. Hi, I have a one piece that is really big on the bottom. How would I fix it so it doesn’t gap and sag? I’ve lost a lot of weight and my butt was second to go. LOL. Can I also take in sides for it being big around waist, armpits and stomach?

    • Hi Melissa – apologies for my delay in responding! You can take in the side seams. Just trim and zig zag or overlock the seams. If it were just the bottoms, depending on how much too big they were, you could re-do the elastic to be tighter and that would help too. Hope you find a solution and congrats on the weight loss!

      • Thank you I will try that. I ended up buying a tankini but I was falling out the top so ended up sewing that. They just don’t make the cups big enough. I’ve lost over 250lbs and I really like my other suit better because it is chlorine proof.

  24. Hi Jaime! I commented already, but I’m not sure if the comment was sent, so I’m trying again. Sorry if this is a double comment! Lol. I’m 5’9″ and 127 lbs with a 27 inch waist, and 37 inch hips, but I bought a swim suit online that is an Asian size Large and the leg holes are too tight on me. The butt is too tight as well, and gets sucked in a bit, but the most unflattering part is that the leg holes squeezing my thighs in and making them look like they’re spilling out. I tried altering the bottoms myself by adding more material to the sides of the bottoms, and I just destroyed the bottoms. So, I tried buying the suit again, this time in an extra large, but it is hardly bigger. The same problem exists. I love the style of this suit so much and know it could be flattering if it just fit me right! Is there anything I can do to make the leg holes fit me right? Thank you!

    • Hi Shelby, I do not see a double comment from you, so no worries! Sorry if you had trouble commenting! It is a lot of work, but I wonder if you could have success in removing the elastic from the leg holes and then replacing it with a longer piece of elastic so it’s not so tight. Or what style is the swimsuit? Is there enough excess fabric from the 2nd suit to make your own bottoms from a pattern?

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