If you have a skirt that doesn't fit quite right and is in need of just a minor alteration, you can do this fairly easily at home with a basic few sewing tools. Altering the waistband of a skirt or replacing it with elastic will prevent you from having to retire a favorite garment due to poor fit. Depending on the style of skirt, and how much you need to alter it, the project can be quite simple or a little more tricky. There are a few different approaches to consider.
Replace the Waistband with Elastic
Remove the skirt's original waistband using a seam ripper. To do this, poke the blade of the seam ripper into the stitches where the waistband is sewn to the skirt. Cut through a few stitches at a time, taking care not to cut the fabric. When you've cut through the stitches, gently tug the waistband away from the skirt, and pull away the loose threads.
Once the waistband has been removed, you can sew in some wide elastic. To do this, cut the elastic to the right size for your waist, sew the ends together to create a loop, and pin the elastic loop around the edge of the skirt where the original waistband was. Fold the top of the skirt over the elastic and using a zigzag stitch on a sewing machine or by hand, sew the elastic in where the waistband used to be. You will probably have to stretch the elastic a little as you sew.
Insert a Wedge of Fabric
If you remove the waistband and realize that the skirt still requires significant alteration, you can add a piece of wedge-shaped fabric to your skirt to widen the waist even more. Try to find a fabric that matches the skirt fabric in color, weight and texture as closely as possible.
Use a seam ripper to unpick the seam in the center-back of the skirt by at least 6 inches. Next, decide how large a piece of fabric you need. The easiest way to do this is to try on the skirt and use paper to trace the shape of the opening you want to fill. Use a ruler to turn the shape into a neat triangle, add a seam allowance, and cut out the shape. Pin the paper piece to your fabric and cut around the sides.
Pin and stitch the new piece of fabric into the open seams of your skirt, making sure to keep the cut edges on the inside of the skirt. You can do this by hand or with a sewing machine. To finish, reattach the waistband. If the waistband is too short you can replace it with elastic as described above.
Let Out the Darts or Pleats
If your skirt has darts (triangular folds sewn along their length) or pleats (straight folds sewn only at the waist) for shaping, you can let them out to make the skirt wider at the waist.
To let out darts, use a seam ripper to pull out the stitches that are holding the darts together. Measure how much the waistband needs to be increased and divide that length equally between the darts. This will let you know how much of the dart to let out. For instance, if you have two darts on the skirt and you need an extra 2 inches of fabric around your waist, each of the darts will need to be reduced by 1 inch. Once you have pulled out the stitches holding the darts together, refold the darts but use 1 inch less fabric for each fold. Then, using a sewing machine or by hand, stitch the dart folds back together.
To let out pleats, unpick the stitches that are holding the pleats in place at the waistband and unfold the fabric so that it's wide enough to go around your waist. Replace the waistband with elastic as described above.