Today, the lack of customisation in retail sizing often necessitates tailoring, and dress alterations can be fairly simple for those with a little sewing experience. Strapless dresses, in particular, are much more easily altered than types with sleeves and high necklines, especially if they do not include too many complex accessories. To learn how to alter strapless dresses for size and style, complete the following instructions.
Determine what type of alteration your strapless dress needs. Usually, strapless dresses are taken in or out at the side seams to change the waist or hip measurements, taken up or down at the hem to change the length, and cut at the bust to increase or decrease the bust measurement. You will only be able to increase measurements slightly, depending on the length of the seam allowances inside the dress, so most dresses must be altered to be smaller.
Alter the dress at the side seams. Put the dress on your body inside out and pinch the fabric in at the waist, hips and bust until the fit is better. Pin the pinches in place, then take the dress off. Adjust the pins so that you are taking off the same amount of fabric from each side of the dress. Using a fabric pencil, draw a smooth line on each side starting below your lowest pins, all the way up to your highest pins, at the point where you want to take the dress in. Pull out the side seam stitches with the seam ripper, then pin your fabric together more securely. Stitch the side seams along your drawn lines.
Change the hemline at the bottom of the dress. Tear out the existing hem stitching with a seam ripper, then put the dress on inside out and have a friend help you mark out a new hemline with pins. Take the dress off, and measure the distance between the edge of the fabric and the pins. Pin up the bottom edge of the fabric to the new hemline and machine stitch the hem in place.
Alter the dress at the bust. Take apart any seams at the front bodice, such as princess seams or underbust seams, and take them in or let them out, as necessary. If your cup size measurement is much smaller than the dress, you may need to insert a princess seam running over the centre of the cup, or a dart in the same place. You may also need to fold down the top hem, if the top of the dress goes up too high. To alter the bust for a larger cup size, take out any darts and let out any princess seams.
Add sleeves to the dress, if desired. You can attach sleeves to a strapless dress by tacking them to the side seams at the top, or by sewing the sleeve ends inside the dress at the front and back. Common types of sleeves for this style of dress are spaghetti straps, halter straps and off-the-shoulder straps.