Finding the right fit is very important! That's why it's even more important to find out what your bust and waist measurements are. Once you know what your measurements are, you will be able to select the right size for you.
Keep in mind formal/couture dresses run smaller than normal dresses. Each designer tends to have a specific size guide, and not all designers follow size guides you would normally refer to for sizing.
We highly recommend reviewing the size guide listed on the specific designer dress brand of your choice before making your special occasion dress purchase. As a general rule when in doubt of a size option, always choose the larger size. It's easy to take a dress in, but nearly impossible to add width.