The size 12 years in American Apparel is closest to the following:
Brand Label Weight (lbs) Height (inches)
American Apparel 12 years 62 - 75 lbs 55 - 59 inches
H&M 7-8 years - 50 inches
Hanna Andersson 140cm 62 - 80 lbs 54 - 58 inches
Hatley 10 - 56 inches
J.Crew/ Crewcuts 8 63.5 - 70 lbs 52 - 54 inches
LLBean 10-12/M - 53 - 58 inches
Marimekko 11 yrs/ 146 cm - 58 inches
MiniBoden 11y - 57.5 inches
Ralph Lauren 10/ M 63 - 73 lbs 54.5 - 56 inches
tea 8/L 61 - 72 lbs 51 - 54 inches