Mermaid-style dresses have become extremely popular for formal wear, particularly in the wedding dress industry. This dress style is called mermaid because of the shape of the skirt, which fits snugly over the legs and fans out at the calves, mimicking the shape of a mermaid's tail. The bodice of a mermaid style dress can have any design although it is often a strapless or camisole style in wedding dresses. You can make your own mermaid-style dress by attaching any bodice style to this mermaid skirt.
Find a basic sheath skirt pattern or sheath dress pattern that you will alter into a mermaid style. This pattern will have several panels that create the sheath shape of the skirt. Cut the pattern pieces for your measurements.
Cut the skirt panels off at knee length, or at the length you would like the fanned part of the mermaid dress to begin.
Pin the skirt or dress pattern pieces to the dress fabric. Cut the pieces from the fabric following the directions on the pieces.
Unpin the pattern pieces from the fabric pieces. Pin the skirt panels together along the long edges, right sides together.
Sew the skirt panels on the sewing machine, using the directed seam allowances. Iron the seam allowances flat. If you are working with a full dress pattern, sew the bodice together as directed in the pattern instructions.
Measure the circumference of the skirt bottom. Multiply this measurement by 2 1/2.
Measure the distance from the skirt bottom to the floor. Add 1 1/2 inches to this measurement.
Cut a rectangle from your dress fabric according to the measurements you just took.
Pin the short edges of the rectangle together, right sides touching. Sew the edges together 1/2 inch away, then iron the seam allowances flat.
Turn under one of the long edges of the rectangle 1/2 inch, then another 1/2 inch. Sew along the fold line and iron the fabric flat.
Sew a gather stitch to the other long rectangle edge, 1/4 inch away from the edge. Sew another gather stitch 1/4 inch away from that stitch line.
Pull the gathers so that the edge of the rectangle fits the bottom edge of the skirt. Pin the rectangle edge to the skirt edge, right sides together.
Sew the gathered rectangle to the bottom edge of the skirt. Iron the seam allowances toward the skirt, and pull out the gather stitches.
To sew a gathering stitch, adjust your sewing machine to the lowest possible setting. Then sew two parallel rows of stitching, allowing the fabric to gather up and create volume. Finally, keep it all in place by stitching between the rows on a higher setting.
Cut the "tail" section wider or narrower depending on the weight of your fabric and how gathered you want it to be when it is finished.
Hem the dress after fitting it to achieve the perfect length.