Most dress manufacturers provide size charts to aid in choosing the correct size. Be sure to measure carefully as size charts are helpful, but not always perfect. Remember that you can always take in a gown that is too large, but it is not always possible to let it out if you order a size that is too small. If your measurements are on the border it is usually better to take the larger size and plan on having it altered. Most girls need alterations to get a perfect fit.