DIY Swimsuit for All Your Summer Splashing

Two-Piece Reversible Swimsuit With Sunglasses and Flip Flops
Mollie Johanson
Overview
  • Yield: 1 swimsuit
  • Skill Level: Intermediate

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.

Halter-Top Two-Piece Swimsuit
Mollie Johanson

Tip

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

What You'll Need

Equipment / Tools

  • Pair of well-fitting underwear
  • Pencil
  • Scissors
  • Pattern weights or clips
  • Sewing machine
  • Needle
  • Measuring tape
  • Rotary cutter
  • Cutting mat
  • Large ruler

Materials

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

Instructions

  1. Draft the Bottom Pattern: Back

    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 your 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 a seam allowance on the folded edge or at the crotch.

    black underwear on white paper by pencil
    Mollie Johanson
  2. Draft the Bottom Pattern: Front

    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.

    Black underwear folded in half on white paper
    Mollie Johanson
  3. Cut Out the Bottom Pieces

    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.

    scissors next to a fabric cut out
    Mollie Johanson
  4. Sew Around the Leg Holes

    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.

    Tips

    • 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.
    • 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.
    swimsuit bottoms being put together
    Mollie Johanson
  5. Sew the Matching Sides

    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.

    Attaching the sides of the bottom swimsuit piece
    Mollie Johanson
  6. Mark the Top Edge of the Bottoms

    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.

    Swimsuit bottom with top edges marked
    Mollie Johanson
  7. Roll the Bottoms for Sewing

    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.

    Clipped swimsuit bottoms
    Mollie Johanson
  8. Sew the Top Edge and Turn

    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 turning swimsuit bottom
    Mollie Johanson
  9. Hand Sew the Opening Closed

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

    A needle next to swimsuit fabric
    Mollie Johanson
  10. Sew the Strap for the Top

    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.

    DIY swimsuit strap on white background
    Mollie Johanson
  11. Cut the Swimsuit Top Pieces

    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.

    Cutter on top of swimsuit material
    Mollie Johanson
  12. Sew the Swimsuit Top Pieces

    Match the bottom edge of a triangle from each fabric and sew. Measure and mark 1 1/2 inches 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.

    Triangular pieces of fabric clipped together
    Mollie Johanson
  13. Hand Sew the Edges at the Openings

    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 the openings, stitching with a double running stitch

    A needle and white thread next to swimsuit fabric
    Mollie Johanson
  14. Head out Into the Sun in Your New Swimsuit

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

    Halter-Top Two-Piece Swimsuit
    Mollie Johanson