My daughter normally wears a small but we had to get this in a medium & it was perfect, so Id size up especially if you're in between sizes. She has long arms and the sleeves were still plenty long enough. For reference, she is 125 pounds and 53 tall & a 32C. She wore this as part of her Sebastian costume for her school play, Little Mermaid Junior. She looked absolutely adorable!!! She got so many compliments! The material is so soft and its the perfect true shade of red! Its truly amazing quality; nice and thick and just a little stretch.