Resize Your Swimwear: How To Tailor A Swimsuit For the Best Fit

Can you tailor a swimsuit? Yes, absolutely! You can tailor a swimsuit to get the perfect fit. How to tailor a swimsuit involves simple sewing steps like adjusting straps, taking in seams, or changing leg openings. What is swim fabric? Swim fabric is usually a stretchy material like spandex or lycra blend that moves with your body. This guide will show you how to make common swimsuit alterations to fix fit problems and make your swimwear more comfortable.

How To Tailor A Swimsuit
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Why a Perfect Swimsuit Fit Matters

Wearing a swimsuit that fits well feels great. It stays in place. It looks better. It makes you feel more confident. But sometimes, swimwear doesn’t fit just right off the rack. Straps might be too loose. The bottom might be too big. The top might not give enough support. Instead of buying a new one, you can fix the one you have. Learning how to tailor a swimsuit can save you money and give you a suit you love. It’s your personal swimsuit alteration guide.

Getting Ready: What You Need

To alter a swimsuit, you need a few specific tools. Working with spandex is different from working with cotton. Spandex is very stretchy. Your tools and sewing techniques for swimwear need to handle this stretch.

Tools for Swimsuit Alterations

Here are the things you will need:

The swimsuit: The one you want to fix.
Sharp Scissors: Fabric scissors are best. Small snips are good for threads.
Stretch Needles: These needles have a rounded tip. They push between the fabric fibers instead of poking holes. This stops the fabric from running or getting damaged. Make sure you get the right size for your fabric.
Ballpoint Needles: These also work well with knit and stretchy fabrics. They are good for machine sewing.
Polyester Thread: Use strong thread that has some stretch. 100% polyester thread is a good choice. It won’t break when the fabric stretches.
Pins or Fabric Clips: Pins can snag delicate swim fabric. Use fine, sharp pins, or use fabric clips. Clips hold the fabric without poking holes.
Measuring Tape: To measure where to make changes.
Seam Ripper: To carefully undo old stitches.
Sewing Machine (Recommended): A machine makes the job faster and stronger. Make sure it has a zig-zag stitch or other stretch stitches.
Optional: Serger Machine: A serger makes very clean, stretchy seams. It cuts and sews the edge at the same time. It’s great for swimwear but not required.
Matching Swim Fabric Scraps: If you need to add fabric or make new parts.
Matching Swim Elastic: If you need to replace or add elastic for support or shape.

Prepping Your Swimsuit

Before you start sewing, wash your swimsuit. Use the same way you usually wash it. This is important. Some fabrics might shrink a little the first time they are washed. Also, washing removes any oils or finishes from making the suit. These can affect sewing. Let it air dry completely.

Next, look closely at the swimsuit. Where does it not fit well? Pin the areas you want to change while you are wearing it, if you can. This helps you see exactly how much needs to be taken in or let out. Take the suit off carefully with the pins still in place.

Taking Measurements for Adjustments

Knowing where the fit is wrong is the first step in adjusting swimwear size. Measure the areas you plan to change.

Straps: How much shorter do they need to be? Pinch the extra fabric and measure.
Bust: Does the top gap? Do you need more coverage? Measure how much fabric you need to add or remove at the sides or under the bust.
Waist/Torso: Is the one-piece too long or too wide? Pinch the extra fabric at the sides or up and down the middle.
Hips/Bottom: Is the bottom too big or too small? Does the leg opening gap? Pinch the extra fabric at the sides or legs.
Leg Opening: Is it too loose or too tight? Measure how much tighter the elastic needs to be, or where you might need to let it out.

Write down your measurements. This is your plan for making a swimsuit smaller or making other changes.

Common Swimsuit Alterations Explained

Many fit problems can be fixed with a few simple changes. Here are some common alterations you can make:

Making a Swimsuit Smaller

This is one of the most asked-about changes. Swimsuits can stretch out over time or just be too big when you buy them.

Taking in Side Seams: This works for one-pieces or bikini bottoms. You sew a new seam inside the old one to make the suit narrower.
Shortening Straps: This helps lift the bust and make the top feel more secure. It’s a common fix for bikini tops or one-pieces.
Adjusting Leg Openings: If the leg holes are too loose, they can gap. You can make the elastic tighter here.

Adjusting Swimwear Size: Bikini Fit

Altering bikini fit involves working with two separate pieces.

Bikini Top: You can shorten straps, take in the band around the back, add padding, or change the shape slightly. Fixing swimsuit gaps in the top usually means taking in the sides or adding more support.
Bikini Bottom: You can take in the side seams, reduce the rise (how high it sits), or make the leg openings tighter. Making a swimsuit smaller often starts with the bottom sides.

Adding Support to Swimsuit

Lack of support is a common issue, especially in bikini tops or one-pieces for larger busts.

Adding Elastic: Sewing strong elastic under the bust or along strap edges adds lift and support.
Adding Padding: You can sew in bra cups or add a pocket to insert removable pads.
Adding a Shelf Bra: For one-pieces or tankinis, you can sew in a simple fabric shelf with elastic for extra bust support.

Fixing Swimsuit Gaps

Gaps can happen at the bust, under the arms, or at the leg openings.

Bust Gaps: Taking in the side seams of the top or adding elastic to the top edge can help.
Armhole Gaps: Taking in the side seams near the armpit or adjusting straps helps.
Leg Gaps: Making the leg opening elastic tighter is the main way to fix this.

Deciphering Swim Fabric: How To Sew Swim Fabric

Working with spandex and other swim fabrics needs special care. They are slippery and stretchy. They can easily snag or stretch out of shape while you sew. Using the right sewing techniques for swimwear is key.

Working with Spandex

Spandex stretches in two or four directions. This is what makes swimsuits fit so well and move with you.

Don’t Pull: Try not to pull or stretch the fabric while you sew. Let the machine feed the fabric through.
Use the Right Needle: As mentioned, stretch or ballpoint needles are a must. A universal needle will damage the fabric.
Use the Right Stitch: A straight stitch does not stretch. It will break when the fabric stretches. You need a stitch that stretches.

Sewing Techniques for Swimwear

The stitches you use are very important.

Zig-zag Stitch: This is the most common stretch stitch on a regular sewing machine. A narrow zig-zag (like 0.5mm wide, 2.5mm long) looks almost like a straight stitch but stretches. A wider zig-zag is good for finishing edges or sewing elastic.
Triple Stretch Stitch: Some machines have this. It looks like a straight stitch but goes back and forth slightly. It’s very strong and stretchy.
Serger Stitch: A serger makes a special stitch that wraps around the edge of the fabric. This stops fraying and creates a very strong, stretchy seam. It’s ideal for swimsuit seams but not everyone has one.

Thread Tension

Proper thread tension is important when sewing stretchy fabric. If the tension is too tight, the stitches won’t stretch, and the seam might pucker. If it’s too loose, the stitches will be weak. Test your stitch on a scrap piece of your swimsuit fabric first. Adjust the tension until the stitches look good and stretch with the fabric.

Step-by-Step: Making Common Alterations

Let’s look at how to do some of the most common swimsuit fixes. Remember to test on scraps first!

Adjusting Straps

This is a simple way to improve fit and adding support to swimsuit tops or one-pieces.

Method 1: Shorten Fixed Straps

Put the swimsuit on and pin how much shorter the straps need to be. Pin the extra fabric together.
Take the swimsuit off. Measure the pinned amount on each strap. Mark this amount.
Decide where to make the change. The easiest place is usually at the back where the strap meets the suit body.
Carefully cut the strap at your chosen spot. Leave a little extra fabric on each piece (about 1/2 inch).
Overlap the two ends of the strap by the amount you measured to shorten. For example, if you needed to shorten by 2 inches, overlap them so the strap is now 2 inches shorter overall.
Sew the ends together using a zig-zag stitch. Sew back and forth a few times to make it strong.
Cover the raw edges. You can fold one edge under the other and stitch again, or cover with a small piece of matching fabric.

Method 2: Add Adjustable Straps

If your straps aren’t adjustable, you can make them so. This requires strap sliders and rings (like on bra straps).

Cut the existing straps.
Attach one end of the strap to a ring, folding the fabric over the ring and sewing it down. This ring will attach to the back of the suit.
Take the other piece of the strap. Thread it through a slider. Then thread it through the ring you just attached. Then loop it back through the slider.
Sew the raw end of this strap piece down onto itself near the slider. This creates the adjustable loop.
Sew the remaining end of the strap (with the slider and ring) to the back of the swimsuit. Sew the other strap piece (just with the ring) to the back of the suit.

This is part of customizing your swimsuit for a better fit.

Taking in Side Seams (Making a Swimsuit Smaller)

This works for bikini bottoms or one-pieces.

Put the swimsuit on inside out. Pinch the side seams to see how much fabric you need to remove. Pin along the new line. Remember, you are making the whole side smaller, so you’ll pinch half the amount on each side seam. For example, if you need to make the suit 2 inches narrower around the waist, pinch 1 inch on each side seam.
Take the suit off. Draw a line with chalk or a washable marker where you pinned. Taper the line smoothly from where you start sewing (maybe under the arm on a one-piece, or the top edge on a bottom) down to the original seam line. You don’t want a sudden bump.
Sew along the line you drew using a zig-zag or stretch stitch. Start sewing a little bit before your line begins and sew a little bit after it ends, smoothly joining the new seam to the old one.
Try the swimsuit on inside out. Check the fit. If it’s good, trim the extra fabric outside your new seam, leaving about 1/4 to 1/2 inch seam allowance.
Finish the raw edge. You can use a wider zig-zag stitch or a serger stitch next to your new seam to keep the fabric from fraying, although knit fabrics don’t fray much.

Adjusting Leg Openings (Fixing Swimsuit Gaps)

If the elastic in the leg opening is too loose, the fabric can sag or gap. You can make the elastic tighter.

Turn the swimsuit inside out. Look at the leg opening edge. You will see the fabric is folded over and stitched down, making a channel for the elastic.
Carefully unpick a small section of stitching (about 1/2 inch) on the inside of the leg opening. Be careful not to cut the elastic.
Find the elastic inside the channel. It might be stitched down in a few places.
Pull the elastic out through the small opening you made. Pull out a few inches.
Try the swimsuit on (carefully!). Pull the loose elastic end until the leg opening feels snug but not too tight. Pin the elastic where it feels right.
Take the suit off. Measure how much overlap there is on the pinned elastic ends. This is how much you need to shorten the elastic. For example, if the ends overlap by 1 inch, you will cut off 1 inch from the elastic.
Thread the elastic back into the channel until the ends meet at the opening.
Overlap the elastic ends by the amount you measured to shorten (e.g., 1 inch). Sew the elastic ends together using a strong zig-zag stitch. Sew back and forth several times. This seam needs to be very strong.
Gently pull on the fabric edge to draw the elastic seam back into the channel.
Stitch the small opening in the fabric channel closed using a matching thread and a zig-zag stitch.

This process is key for many women’s swimsuit bottoms or the legs of one-pieces when adjusting swimwear size.

Altering Bikini Fit: Taking in the Back Band

If the band around your chest on a bikini top is too loose:

Put the top on. Pinch the extra fabric at the center back (where the tie or clasp is) or at the side seams. Pin the amount to remove. If using a clasp, it’s easier to alter at the sides.
Take the top off. If altering at the back clasp, simply measure the overlap you pinned. Cut the excess fabric off each side of the clasp area, leaving a small amount for seam allowance. Re-attach the clasp ends using a strong zig-zag stitch, overlapping the fabric and sewing securely.
If altering at the side seams, mark the amount to remove on each side seam. Taper the line from the underarm down to the bottom edge of the band.
Sew along the marked lines with a zig-zag or stretch stitch.
Trim the excess fabric, leaving a small seam allowance. Finish the raw edges if needed.

This helps with adding support to swimsuit tops and getting a better fit.

Adding Support & Customizing Your Swimsuit

Beyond just making things smaller, you can add features. Customizing your swimsuit makes it truly yours and can improve comfort and fit.

Adding Bra Cups or Padding

This is a popular way to add shape and support.

Method 1: Sewing in Cups Directly

Get swimsuit-specific foam cups or bra pads.
Turn the swimsuit top inside out.
Position the cups where you want them over the bust area. Make sure they are centered and level.
Pin the cups in place around the edges.
Hand-sew the cups to the swimsuit lining (if it has one) or the inside of the fabric using a simple needle and thread. Use a loose stitch that won’t show on the outside. Sew around the top, bottom, and sides of the cups.

Method 2: Creating a Pocket for Removable Pads

This is better if you want to take the pads out for washing or changing the look.

Get your desired swimsuit pads.
Cut two pieces of matching swim fabric (or lining fabric) slightly larger than the pads. These will be your pockets.
Finish the top edge of each pocket piece (the edge that will be open). You can fold it over and stitch or use a zig-zag.
Turn the swimsuit top inside out. Position the pocket pieces over the bust area where you want the pads to sit. The finished edge should face towards the top of the suit.
Pin the pocket pieces in place.
Sew the pocket pieces to the swimsuit lining or fabric along the sides and bottom edges using a zig-zag stitch. Leave the top edge open.
Insert the pads into the pockets.

Adding Elastic for More Support

Sewing elastic under the bust line in a tankini or one-piece can add significant support.

Turn the swimsuit inside out.
Decide where you want the elastic to sit (usually right under the bust). Mark a line.
Cut a piece of swimsuit elastic. Make it slightly shorter than the width of the suit at that point. Stretch elastic adds tension. The right length depends on how much stretch the elastic has and how much support you want. Start with the elastic length about 85-90% of the suit’s width.
Pin the elastic to the inside of the swimsuit along your marked line. Stretch the elastic slightly as you pin it so it lays flat against the fabric. Distribute the stretch evenly.
Sew the elastic to the swimsuit using a wide zig-zag stitch. Stitch along both the top and bottom edges of the elastic for a strong hold. Stretch the fabric slightly as you sew to match the elastic’s length.

This is a key technique for adding support to swimsuit styles that lack structure.

Swimsuit Alteration Guide: A Quick Checklist

Before you start altering bikini fit or making any swimsuit smaller, run through this list:

Wash and dry the swimsuit.
Inspect the suit and decide exactly what needs changing.
Measure the areas for alteration.
Gather all your tools: stretch needles, polyester thread, pins/clips, scissors, sewing machine.
Test your stitch on a fabric scrap. Use a zig-zag or stretch stitch. Check tension.
Plan your steps before cutting or sewing.
Work slowly and don’t stretch the fabric as you sew.
Try the suit on inside out after stitching to check the fit.
Trim excess fabric carefully.
Finish raw edges if needed.

This guide covers many common issues when adjusting swimwear size and customizing your swimsuit. Remember, practice makes perfect when working with spandex!

Advanced Tips for Working with Swimwear

Working with Linings: Many swimsuits have a lining. When you take in seams, you will often sew through both the outer fabric and the lining together. Treat them as one layer. If adding support or pockets, you often sew only to the lining so the stitches don’t show on the outside.
Using Different Elastic: There are different types of elastic. Rubber elastic is often used in swimwear edges. It has great recovery (bounces back well). Clear elastic is also used and is less bulky. Choose elastic that is meant for swimwear.
Finishing Edges: A serger gives the best finish. If you don’t have one, a wide zig-zag stitch along the raw edge will help. Or, you can fold the raw edge under and stitch it down for a clean finish on the inside, but this adds bulk.

These sewing techniques for swimwear help you get a professional-looking result.

Troubleshooting Common Problems

Puckering Seams: This usually means your stitch isn’t stretchy enough, your thread tension is too tight, or you are stretching the fabric as you sew. Try a wider or longer zig-zag stitch, loosen tension, or handle the fabric more gently.
Skipped Stitches: This is often caused by the wrong needle. Make sure you are using a stretch or ballpoint needle that is sharp and the right size.
Elastic Showing Through: If you added new elastic, make sure it’s fully inside the channel or sewn down securely. Check that your stitching is catching the elastic.

Frequently Asked Questions (FAQ)

Q: Can I make any swimsuit smaller?
A: Most swimsuits can be made smaller, especially simple styles like basic bikini tops and bottoms or classic one-pieces. Very complex suits with lots of cutouts or special features might be harder to alter.

Q: What kind of sewing machine stitch should I use?
A: You must use a stitch that stretches. A regular straight stitch will break. A zig-zag stitch is the most common choice on a regular sewing machine. A serger machine makes a great stretch stitch.

Q: Do I need a special sewing machine?
A: No, you don’t need a special machine. A standard sewing machine that has a zig-zag stitch will work. Using the right needle (stretch or ballpoint) and thread (polyester) is more important than having a special machine.

Q: Can I let out a swimsuit that is too small?
A: This is much harder than making one smaller. Swimsuits often have small seam allowances. There might not be enough extra fabric inside the seams to make the suit bigger. If a swimsuit is too tight, it’s often better to start with a new one or use fabric scraps to add panels, which is a more complex alteration.

Q: How do I sew elastic onto swim fabric?
A: Use a zig-zag stitch. Pin or clip the elastic to the fabric edge (or inside a channel). Stretch the elastic slightly as you sew it down with the zig-zag stitch. The stitch needs to be wide enough to catch the elastic and allow it to stretch.

Q: Where can I find swimsuit elastic and fabric?
A: Fabric stores that sell sewing supplies usually have swimsuit fabric and elastic. Look for fabrics labeled lycra, spandex, or 4-way stretch knit. Look for elastic labeled “swim elastic” or “rubber elastic.”

Learning how to tailor a swimsuit is a useful skill. It lets you fix fit issues and makes your swimwear last longer and feel better. With the right tools and simple sewing techniques for swimwear, you can adjust swimwear size, fix swimsuit gaps, add support to swimsuit tops, and enjoy a perfectly fitting suit. Get out your sewing kit and start customizing your swimsuit today!