DIY Swimsuit for All Your Summer Splashing

Two-Piece Reversible Swimsuit With Sunglasses and Flip Flops
Mollie Johanson

Create Two Bikinis in One!

Halter-Top Two-Piece Swimsuit
Mollie Johanson

Can't find the bikini you're looking for? Make one instead! This DIY swimsuit is easy to sew and you can choose exactly the fabrics you want. Plus, it's reversible, so you don't even have to decide between two colors or prints! 

Sewing swimwear is easier if you have a serger, but this tutorial shows you how you can sew stretchy fabrics on a standard sewing machine with a stretch zig zag stitch.

Tools and Supplies

Supplies for Making a Swimsuit
Mollie Johanson


  • 2/3 yard swim fabric A
  • 2/3 yard swim fabric B
  • Large paper
  • Polyester thread


  • Favorite pair of well-fitting underwear
  • Pencil
  • Scissors
  • Pattern weights or pins
  • Sewing clips or pins
  • Sewing machine
  • Needle
  • Measuring tape
  • Rotary cutter, cutting mat, and large ruler 

Note: For this tutorial, the fabric in the sample has a 50% four-way stretch. Working with a different stretch swimsuit fabric may give different results.

Draft the Bottom Pattern: Back

black underwear on white paper by pencil
Mollie Johanson

To make the pattern piece for the bottom of the swimsuit, trace a long straight line on your paper. This is the fold line. Fold a pair of underwear in half, lay the folded edge on the fold line and trace around it on your paper.

Add 3/8-inch for seam allowance on the top, side, and leg hole. You don't need to add seam allowance on the folded edge or at the crotch.

Draft the Bottom Pattern: Front

Black underwear folded in half on white paper
Mollie Johanson

Refold the underwear so that it's only folded along the front center. Place the folded edge on the fold line with the crotch lining up with the crotch from the traced back piece.

Again, add the seam allowance like in the previous step.

Cut Out the Bottom Pieces

scissors next to a fabric cut out
Mollie Johanson

Cut out the paper pattern piece and lay the fold line on the folded edge of your fabric. Cut out one piece from fabric A and one from fabric B. 

You can use scissors or a rotary cutter for this step.

Sew Around the Leg Holes

swimsuit bottoms being put together
Mollie Johanson

With right sides facing, sew around the leg holes, leaving about 1-1/2-inch unsewn on the back of one seam. Sew with a stretch zig-zag stitch and a 3/8-inch seam allowance.

Note: Even though solid swim fabrics look similar on both sides, there's usually a right and wrong side, so be sure to watch for that.

Tip: This fabric is slippery, so it helps to hold it with lots of pins or sewing clips, but a large hand basting stitch also works well.

Sew the Matching Sides

Attaching the sides of the bottom swimsuit piece
Mollie Johanson

Match up the side seams so that fabric A is with fabric A and fabric B is with fabric B. Sew the sides.

Be sure to sew across the seam allowance from the opening you left in the leg seam from the previous step.

Mark the Top Edge of the Bottoms

Swimsuit bottom with top edges marked
Mollie Johanson

Turn the swimsuit bottom right side out. Use sewing clips or pins to mark the top edge of the two front layers. This shows you which fabrics to match up for the next step.

Roll the Bottoms for Sewing

Clipped swimsuit bottoms
Mollie Johanson

Roll the bottom part of the piece, then separate the marked fabrics and bring them around the rolled part. When the marked fabrics meet each other again, everything else should be tucked inside and you should have the right sides facing. 

Line up the side seams again, making sure that the right sides are facing each other. Pin or sewing clip the fabrics together.

Sew the Top Edge and Turn

hand turning swimsuit bottom
Mollie Johanson

Loosely baste the top edge, close to the fabric edge. As you work your way around the top edge, you can pull the rolled part through what is like a tube. Continue adding basting stitches and pulling it through. 

Repeat this same process as you sew around the top with stretch zig-zag stitch. 

Hand Sew the Opening Closed

A needle next to swimsuit fabric
Mollie Johanson

Turn the swimsuit bottom right side out through the gap in the leg hole. Hand sew the opening closed with ladder stitch.

Sew the Strap for the Top

DIY swimsuit strap on white background
Mollie Johanson

To make the top piece, start by measuring around your torso, just under your bust line. Add 12 inches to that measurement.

Using your rotary cutter, cut two strips of fabric 1-1/2 inches wide by the length figured above.

Sew the two strips with right sides facing. Turn the piece right side out and hand sew the end closed.

Cut the Swimsuit Top Pieces

Cutter on top of swimsuit material
Mollie Johanson

Choose how wide you want the bottom of the triangle pieces for the swimsuit top. For the sample, the pieces started at 9 inches wide. You can adjust this based on your size.

Fold the fabric in half and mark 4-1/2 inches away from the fold (or half of whatever size triangle base you're using). On the fold, mark 27 inches up from the base of the triangle.

Use your ruler to cut an angled line from the two markings.

Cut out two triangle pieces from fabric A and two from fabric B. You may want to use the first cut piece as a pattern for the rest of the pieces.

Sew the Swimsuit Top Pieces

Triangular pieces of fabric clipped together
Mollie Johanson

Match the bottom edge of a triangle from each fabric and sew. 

Measure and mark 1-1/2 inch up from the sewn edge on each side of the triangle. Sew from the marking up to the triangle point, then back down to the second marking. 

Leave the two openings. Repeat with the second set of triangle pieces.

Hand Sew the Edges at the Openings

A needle and white thread next to swimsuit fabric
Mollie Johanson

Trim any excess fabric to reduce bulk, then turn the triangle pieces right side out through the side openings. 

Hand sew the raw edges under at the openings, stitching with a double running stitch

Head Out Into the Sun in Your New Swimsuit!

Halter-Top Two-Piece Swimsuit
Mollie Johanson

Slide the strap through the openings on the triangle pieces and your DIY swimsuit is ready to wear!

You can wear this with only one color showing or you can mix and match the top and bottom for a fun and playful look. All you need now is a matching cover-up!