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How to Alter Swimsuit

There are many reasons you may want to alter your swimwear. Perhaps you lost weight or couldn’t pass up that end-of-summer sale on a suit that wasn’t quite the right size. Whatever the reason, it’s especially important that swimwear fits snugly against the body to help avoid embarrassing or awkward mishaps. If you’ve found yourself in this situation, you’re probably wondering how you can alter a swimsuit.

With a little sewing experience, both one and two-piece swimsuits can be easily altered. Suits that are too big can be taken in to adjust their size. Though slightly more limiting, adding additional fabric panels to a suit that’s too small can make it bigger.

In this article, we will go over how to alter swimsuits that are too big, too small or too boring. We will also cover a super simple solution for adjusting swimsuit straps and provide some very helpful tips to use when sewing that slinky swimsuit material.

How to Alter Swimsuit

Can You Alter a Swimsuit?

Swimsuits, just like most articles of clothing, can be altered relatively easily with a home sewing machine. The super stretchy, slinky material can be slightly more difficult to work with than something like cotton. But with a bit of experience – and/or practice – you should be able to make your ill-fitting swimsuit the right size without too much trouble.

Swimsuits that are still in good condition are great candidates for re-sizing. If the swimsuit no longer fits properly because the material has lost its stretch – that’s a different story. You want to make sure that the swimsuit fabric still has its integrity before deciding whether or not it’s worth it to make alterations. A suit stretched thin from years of wear will likely not hold its shape for long, even after being resized.

How to Alter a Swimsuit That is Too Big: Step by Step

Alter a Swimsuit That is Too Big

The most common reason for a swimsuit alteration is that the suit is too big. Thankfully, this is usually the easiest alteration to make as well. In most cases – swimsuits that are too large can be taken in by about one size without making any changes to the pattern’s structure. The easiest way to take in the suit is simply to sew along the original side seams at the point that makes it fit best. Below you will find a step-by-step guide on how to alter a swimsuit that is too big.

  1. Try on the swimsuit. At this point, you should be wearing the suit with no underwear to make sure that you will get the most accurate measurements. You will want to make sure that once you make the alteration, the swimsuit will fit nicely and snugly with no gaping.
  2. Pin the suit. Pins should be placed so that you will take in the same amount on each side. For example – if the suit needs to be taken in by 1 inch, set pins or clips at ½ an inch from the original seam on each side. Alternatively – you can measure your body and use the measurements accordingly to determine where the pins should be placed on the swimsuit.
  3. Turn the swimsuit inside out. When altering a swimsuit, the sewing should be done from the inside of the suit to produce a professional-looking finish.
  4. Set the machine. Because stretch is of utmost importance in swimwear, it is important to use a loose zigzag stitch when sewing. This will ensure that the stitches don’t pop when the suit is stretched to be put on or taken off.
  5. Sew along the lines of the original seams. Now, all you have to do is sew along the entire line where the original side seams were sewn! Be mindful of your stitch path – don’t simply sew in a straight line. Make sure you follow any curves of the suit’s shape. If you’re working with a bikini top that doesn’t have seams, choose a place below the shoulder to create one and follow the natural line of the bathing suit.

Note* If you are working with a piece that has darts or details at the front – most often along the bust line of the swimsuit – it is important to keep these areas intact. Sewing over these areas could compromise the fit of the suit. If this is the case – before sewing the seam, fold the fabric using material from the back of the swimsuit, then sew it together right along the original seam. Another instance where it is important to sew material from the back of the suit is when there are pockets or openings for support pads. You don’t want to sew these holes shut – leaving you with no way to remove or reinsert the pads.

If you are dealing with leg openings that are gapey, an easy fix is to sew in elastic. Choose a thin, flat cotton elastic – this can even be specific to swimwear – and cut it to a size that will be snug, but not tight, around your leg. Using a loose zigzag stitch – sew the elastic to the wrong side of the swimsuit leg opening, starting at the front of the suit. While sewing the front side, the elastic should lie flat against the swimsuit material – or lining – and be taut but should not be pulled. Once you come to the backside, there will be significantly more swimsuit material than elastic. Gently stretch the suit material along with the elastic and sew in place evenly until you meet the other end. This will create obvious bunching that will be pulled tight and snug against your skin once the suit is put on.

Altering a Bathing Suit That’s Too Small

Altering a Bathing Suit Too Small

Altering a swimsuit that’s too small is a bit less straightforward since swimsuits don’t contain extra material that allows them to be let out like many other garments. That doesn’t mean it’s not possible! The best way to increase the size of a swimsuit that’s too small is by adding additional panels of material. The good news is that you can get creative and use it as an opportunity to breathe new life into the suit.

When choosing fabric for swimwear, selecting material with 2-way or 4-way stretch is crucial so that the garment can be put on easily but will still fit snug all around. Try and match the new material’s stretch with the original suit’s material. You could easily add material in the same color for a discreet alteration or consider adding panels of lace or sheer material for something more sultry. Contrasting or complementary colors can be used, or you could add a fun pattern to an otherwise solid suit. The easiest way to place the panels is between already existing seams. Cut the seams and turn the suit inside out. Sew your new panels – cut to the appropriate measurements for your body – in the space between the old seam using a zigzag stitch. Voila!

How to Alter Swimsuit Bottoms

There’s nothing more uncomfortable than a swimsuit bottom that doesn’t fit right! Whether it’s too large and won’t stay up, or squeezes so tight you want to take it off – misfitting bikini bottoms are a pain. Similar to swimsuit tops – bottoms can be taken in by about one dress size. Alternatively – if the bottoms are too small, additional panels can be sewn into place to make the suit larger.

To alter a swimsuit to make it smaller:

  1. Try on the suit – without underwear – and pin the material on both sides so that it will be comfortable and snug while not too tight.
  2. Turn the swimsuit inside out.
  3. Set the machine to a loose zigzag stitch and sew along the line of the original seam at the appropriate point for your measurements. Make sure that you follow any curves that are in place rather than sewing a straight line. If necessary – the material may be stretched slightly to ensure the edges line up accurately.
  4. Repeat on the other side.

If the bikini bottoms are too loose around the leg, consider sewing in a piece of elastic that will make them fit nicely and snug. Make sure to use flat swimwear elastic and sew with a zigzag stitch to allow for stretch.

If the leg opening falls at an undesirable or awkward spot, hemming them to a more flattering place is pretty simple. Try on the suit and fold the hem at different points until you find the one you prefer. Pin the hem at the desired point, take off the suit bottoms, and sew the new hemline using a zigzag stitch

To alter a swimsuit to make it larger:

  1. Choose a material that will match or complement the material of the swimsuit to be altered.
  2. Measure and cut panels following the size of your measurements.
  3. Cut the seams of the swimsuit bottoms using a seam ripper.
  4. Turn the bottoms inside-out and pin the new panels between the newly cut seams.
  5. Using a zigzag stitch, sew the panels in place.

How to Alter Swimsuit Straps in 4 Easy Steps

Even adjustable swimsuit straps can sometimes be too long – and what is more annoying than constantly pushing up a suit strap that keeps falling?! Thankfully – by following these four steps – altering the straps of a swimsuit is quite easy and shouldn’t take much time.

  1. Using a seam ripper, cut the stitches holding the strap in place at the back of the swimsuit.
  2. Put on the suit and try out different strap lengths until you find one that is just right. Pin the straps and test that they stay put with different movements and positions. The straps shouldn’t put too much pressure on your shoulders while sitting but should not fall at any point.
  3. Using a straight stitch, sew the strap in place on the inside along the top edge of the swimsuit. Sew a second line, about a ¼ inch down from the suit’s seam. When you’re finished sewing, you should have two parallel lines of stitching. Repeat with the other strap.
  4. Cut any excess strap fabric from under the stitching and sew over the raw edge with a zigzag stitch to keep everything tidy and together.

Altering a Swimsuit That’s Too Boring

I’m sure I’m not the only one who’s tempted to buy at least one new swim suit each season – but we all know that’s just not economical. Instead of spending money and resources on unnecessary purchases, consider taking an old suit and making it into something new and exciting! Whether it’s the style or the print that is leaving you pining over something different, there are several ways you can alter a swimsuit to turn it into something you’ll love.

Turn an old one-piece into oh-so-flattering high-waisted bottoms! Try on the swimsuit and mark the spot where you would like the waistline of the new bikini bottoms to lie. This will be about 5 inches from the hip but can vary depending on the suit and the length of your torso. Make sure to leave about an inch of extra fabric for the seam. Once you’ve marked the spot, lay the suit flat – making sure there are no wrinkles – and cut the suit in half. Using a zigzag stitch setting, fold over the raw edge ⅝ of an inch and sew around the entire waistline. You now have a trendy new bikini bottom. Follow the same process for cutting and sewing the top of the suit to complete the set – or mix and match with another complementary top!

Add a little ruching for a cheeky bikini bottom. This simple alteration can take boring bottoms to a new level in minutes! All you need to do is sew a thin, flat swimwear elastic piece on the inside center of the back of the suit. Make sure to pull the elastic tight while sewing – the tighter it’s pulled; the more ruching will be created. You can sew a small section of ruching just near the top or sew the entire length of the bikini bottoms. Use a zigzag stitch so it can be stretched easily without the stitches popping.

Turn a two piece into a one piece. One piece swimsuits are all the rage, so why not turn an old bikini into a fun new one piece? Find a stretchy lace or mesh material to sew between the top and bottoms of a bikini and you’ll find yourself with an entirely new – classy, yet sexy – beach-ready look.

How to Make a Bikini Top Smaller Without Sewing

The best – and most permanent – way to make any swimsuit smaller is by sewing it. If that’s not an option – or you have a swimsuit emergency, a safety pin can save the day in a pinch. While wearing the swimsuit, pull the fabric to the point where it feels comfortable and snug. Fold the fabric in and secure the pin inside the suit. This may be easier to achieve with the helping hand of a friend.

If you have a bikini with too loose straps and don’t have the time or desire to sew them, try cutting the straps loose at the back and then tying them around the neck like a halter. This will give your bikini top a new look, as well as making it adjustable.

How to Make a One Piece Swimsuit Smaller

Perhaps not surprising, making a one piece swimsuit smaller may be one of the easiest swimwear alterations you can make. The process is similar to taking in any other suit – just follow these easy steps:

  1. Try the suit on with nothing underneath and mark the point on each side where you need to take the suit in. If unsure, start with ½ an inch – a ¼ inch on each side. You can always re-sew with a larger seam allowance if the suit is still too big. Fold the fabric over inside and pin or clip it in place.
  2. Set your sewing machine to a zigzag stitch and turn the swimsuit inside out.
  3. Starting from the top of the suit, sew the entire length along the seam until reaching the leg opening.
  4. Repeat on the other side.

Try the suit on and check the new fit. If you still find it’s too loose, you can take it in by another ¼ inch on each side until it fits comfortably. Once it’s just right – you can trim away any excess material on the inside if necessary. If it is only a small amount of fabric, you may want to simply leave it in place.

Tips for Sewing Swimwear

Sewing super stretchy swimsuit fabric can be a doozy, especially if you’re new to sewing. But with a bit of practice under your belt – and these helpful hints at your fingertips – even a novice seamstress should be able to complete alterations on swimwear.

  1. Use polyester thread. Swimwear gets a lot of action – swimming is a sport, after all. But even if you’re just lounging in your swimsuit, the constant stretching to get it off and on can cause a lot of stress. You need a very durable thread when sewing swimwear.
  2. Use a ballpoint or stretch needle in your machine. These needles are specifically designed for knits and stretchy fabrics like swimsuit material. The curved tip of a ballpoint needle allows it to separate and slip between the threads of the fabric – making tangles and breaks much less frequent. Stretch needles also have a special coating that makes them glide through the fabric more easily.
  3. Use clips instead of pins to keep the material together. Even though it’s thin, stretchy swimsuit material can be painful to get pins through. Pins can also easily catch and snag the fabric. For an ideal way to keep your swimsuit textiles in place and looking their best – opt for clips.
  4. Use a zigzag stitch. When sewing something that requires a lot of stretch, a zigzag stitch is imperative. A straight stitch, if pulled, will break, causing stitches to pop and undoing all the work you just did. Unless it’s to secure a strap or something that doesn’t need to be flexible – always use a zigzag stitch.
  5. Test your settings! It is always best practice to test your precise materials and your settings to make sure they’re just right. This will give you the most successful results every time.
  6. Choose man-made materials. Generally, we love all-natural, but when it comes to swimwear, nothing compares to synthetics. The best material for swimsuits will be mostly nylon – 80-90% – with a good amount of lycra and spandex. This type of material won’t hold on to water will be lightweight, comfortable and, snug, as well as supportive.
  7. 2-way or 4-way stretch. The swimsuit material is extra stretchy. Two-way stretch material stretches horizontally – it is less stretchy than 4-way, but still used for swimsuits – usually two pieces. One piece suits will always be composed of 4-way stretch material. This means that the fabric has horizontal and vertical stretch – which is necessary when considering how a swimsuit fits your body.
  8. When using elastic, choose cotton or rubber – swimwear-specific elastic being ideal. These elastics will hold up to chlorine, sun, and water much better than regular elastic – which will degrade and break down much quicker.

Can a Tailor Alter a Swimsuit?

If you don’t want to do the work to alter your own swimsuit, deferring to a professional is always an option. Like any other garment, your neighborhood tailor will have the knowledge and the know-how to get your suit to fit like a glove. But what will this alteration cost you? If it’s a simple fix – like a strap adjustment – it will probably run around $10 and have a quick turnaround time. To take the suit in shouldn’t be too much trouble, but to decrease by anything more than one dress size might make things more complicated. Also, consider that anything with a lining will add additional work and, therefore, an additional expense. More in-depth swimsuit alterations can cost upward of $60, so it’s important to weigh your options – and the overall value of the suit.


Altering a swimsuit, in just about any manner, is well within your reach. Using these easy steps and helpful hints, you can adjust the size of any sort of suit and be on your way to the pool in no time! You may have started out searching for a practical solution for an ill-fitting swimsuit – but who knows what swimwear adventure you’ll go on now that you have so many creative options!