Shortening a formal dress is often left to a professional tailor but with a little practice you may be able to save yourself time and money by shortening your dress at home. According to Dorothy Jump, a seamstress for more than 60 years, completing your project at home is often more affordable and less time-consuming than sitting through multiple fittings with a professional. Remember to start your tailoring project well in advance of your event to allow yourself the time to complete the dress without the finished dress looking rushed.
Put the dress on, and have a helper mark the dress with chalk at the length you would like. Make sure that you make small marks all the way around the dress.
Lay the dress out, and make another mark about 2.5 cm (1 inch) below your original mark. This will give you room for a seam while keeping your original length. If your dress has more than one layer, you will need to pin the layers together.
Trim your dress along the bottom marks you made on the dress. Take your time, so you do not snag the fabric. Make sure you are cutting through all layers of the dress.
Fold the bottom of the dress along the first marks you made, making sure you are folding each layer separately. Pin each layer in place, and iron the fold. Repeat this for every layer of the formal.
Stitch the hem with a small stitch to make the adjustment look professional. After you have hemmed all the layers of the formal, you can go back and trim away any extra fabric on the underside of the dress.
Using scissors made for fabric will help you keep from snagging the fabric.
Speeding through the sewing of your formal can result in the fabric being punched up, so make sure to take your time.