Hello, thank you for your interest. The body measurements of our product for 13-14 year olds are suitable for 158-164 cm height, 81-84 cm chest and 76-79 cm waist range. If your child is petite and thinner than their peers, a size 13-14 will likely fit them well in terms of length. Due to their slim build, it will also offer a slightly looser and more comfortable fit. To choose the most accurate size, we recommend comparing the chest and height measurements in the size chart in the product image with a similar outfit of your child. We wish you pleasant shopping.