The size 12 in J.Crew/ Crewcuts 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 12 76 - 80 lbs 56 - 58 inches
LLBean 10-12/M - 53 - 58 inches
Marimekko 11 yrs/ 146 cm - 58 inches
MiniBoden 11y - 57.5 inches
Ralph Lauren 12/ M 74 - 87 lbs 56.5 - 58.5 inches
tea 10/L 72 - 82 lbs 54 - 57 inches