In general they are true to size. 1-2T runs towards 2T, 2-3T runs towards 3T, and all others are true to size. They are versatile though as well. They are cute fitted and even tea length but also cuter looser and longer.
Oakleigh is around 37 inches and 35 lbs. wearing the 2-3T. Another child approx. 53" 51 lbs. liked the 6-7T.