Designers usually prefer that you get measured for a bridesmaid dress in a bridal salon; however, if you cannot, at least have a friend help measure you. Measurements need to taken with the undergarments and shoes you plan to wear for the wedding. Besides that, it is imperative that you follow measuring guidelines set by designers to ensure the correct fit.
Measure your bustline in a similar fashion that you would if you were taking your bra size. Stand naturally with your feet together and your arms resting at your sides. Measure your bust at the fullest area by placing the measuring tape around the widest section of your back and the fullest part of your chest, allowing room for a thumb inside the tape.
Position the measuring tape at your natural waistline, making sure your stomach is in its proper position as well. Do not pull the measuring tape too tight, and keep a thumb in there for breathing room.
Position yourself naturally with your feet together. If your bridesmaid dress is going to be sheath, place the measuring tape around the fullest part of your bottom. However, if your dress is A-line, measure the fullest area around your hips. Again, do not pull the tape too tight.
Measure for the length of the dress by measuring from the hollow of your neck, located by your collarbone, to your preferred hemline. Most designer dresses measure 57 inches from hollow to hemline. If you are tall, 5'9 or taller and are planning to wear heels in the wedding, you should consider ordering an extra-length dress, which is 5 inches longer than a standard dress.
When you have your measurements, check the corresponding designers' size chart by calling your bridal salon. These charts indicate how the measurements correspond with the designer's sizes. If the chart puts you in one size for bust and another for hips, it is usually recommended to order the larger size, because it is easier to alter a dress to a smaller size than to make it larger.