Being able to let out a waistband on an elasticized waist is a simple sewing project that can save you lots of money on alterations -- and maybe even new clothes. You can usually adjust up to 3 inches in an existing waistband. Stretch out the elastic waist of the garment and make sure there is enough fabric to make it the size you need.
Things You'll Need
Sewing machine with a size 70-75 needle
Elastic, in the same width as the garment being altered
Use a seam ripper at the inside center back of the garment to remove the stitching closing the waistband casing seam, about 2 inches in each direction. Work carefully in a well-lit space.
Remove any stitching found through the elastic around the entire waistband. Frequently you will find a single row of stitching through the waistband elastic in the center of the waistband to prevent rolling -- sometimes more than one, sometimes none.
With the stitching removed, the elastic will pull freely through the waistband. Pull up a section of elastic and pin it on the left and right to prevent it from retracting into the casing. Cut through the elastic.
Cut a piece of elastic the same width as the elastic in the garment and the length you want to extend the waist, usually between 1 1/2 and 2 inches. Set the sewing machine to a wide zigzag stitch and a short stitch length. Unpin one side of the elastic and pull it out enough to maneuver easily. Hold the two pieces of elastic close together, not overlapping, and stitch together with a zigzag stitch catching each side of the elastic.
Sew the elastic together on the opposite end in the same manner, being careful to have the elastic straight, with no twists in it.
Stretch the garment's waistband out, pulling the elastic into the casing. Pin the casing closed, folding it in line with the rest of the waistband.
Sew the waistband closed while pulling the fabric straight. Don't catch the elastic in this seam.
If there was no center stitching through the center of the elastic that you had to rip out, skip this step.
Stretch the waistband and elastic out straight, and stitch through the center of the elastic all the way around the garment. If the garment had several rows of stitching that you had to remove in Step 2, replace those rows as well.
Cut the waistband open to determine the width of elastic size you need.