To alter a dress, take measurements for size and length, and mark them on the dress. Sew the bodice first. Rip out the old hem, cut it to the new length, fold twice, and sew into place.
- Measure for size
Use a measuring tape to take measurements at your waist and hips. Use the tape to measure the front and back of the dress, and add them together. The differences between your measurements and the dress's are how much you need to take it in.
- Measure for length
While wearing the dress, determine where you want the hem to hit. Use sewing chalk to mark this spot in two places.
- Calculate the seam
Start with the difference between your waist and the dress's, and divide it by four. Do the same with the waist difference.
- Mark the seam
Turn the dress inside out. Use a seam gauge to measure in from the outside of the waist seam. Mark with chalk. Repeat this procedure for the hips. Draw a gentle arc starting just below the bust to just below the waist and incorporating the two seam marks.
- Sew the seam
Use a sewing machine or needle and thread to sew along the seam markings.
- Rip out the old seam
Use a seam ripper to carefully rip out the old seam. Press, and finish the edges with a zigzag stitch.
- Start the hem
Use the seam ripper to remove the stitching from the hem.
- Mark the new hem
Use the seam gauge to measure the distance between the bottom of the fabric and the chalk marks. Add 1 inch, and mark this new hem all the way around with the chalk.
- Cut the hem
Lay the dress flat. Cut along the chalk like your just made.
- Fold the hem
Mark 1/2 inch up from the bottom of the dress. Fold at this measurement, and press. Fold up another 1/2 inch, and press.
- Sew the hem
Use a blind stitch to sew the hem in place.