My daughter wears a size 6 (for length) in clothes, however, she is slender and most of her bottoms are usually very loose at the waist (and have to be taken in).  I ordered these hoping they would run small, and luckily they do.  The waist size looks to be about a size 4T.  They are very short, but they should be as they are boy cut shorts. They are great, high quality, stretchy material.