The size 6-7 years in H&M is closest to the following:
Brand Label Weight (lbs) Height (inches)
American Apparel 8 years 49 - 52 lbs 48 - 50 inches
Burt's Bees Baby (Target) 6 48 lbs 45 - 47.5 inches
Carters 5T 38 - 42 lbs 41.5 - 43.5 inches
Cherokee (Target) 7 48.5 - 54 lbs 47 - 48.5 inches
Circo (Target) 7 48.5 - 54 lbs 47 - 48.5 inches
Gap 5T 40 - 46 lbs 42 - 45 inches
Gymboree 5T 41 - 46 lbs 42 - 45 inches
H&M 6-7 years - 48 inches
Hanna Andersson 120cm 45 - 55 lbs 46 - 50 inches
Hatley 6 - 47 inches
J.Crew/ Crewcuts 6 46.5 - 54.5 lbs 45 - 49 inches
LLBean 6X-7/L - 45 - 48 inches
Lands End 7/L 49 - 54 lbs 47 - 49 inches
Marimekko 7 yrs/ 122 cm - 48 inches
MiniBoden 7y - 48 inches
Old Navy 5T 40 - 46 lbs 42 - 45 inches
OshKosh 5T 38 - 42 lbs 41.5 - 43.5 inches
Petit Bateau 8Y 43 - 47 lbs 49.5 inches
Ralph Lauren 6 45 - 49 lbs 46 - 48.5 inches
The Children's Place 0-3 months 7 - 11 lbs -
Tucker + Tate (Nordstrom) 5T 39 - 44 lbs 42 - 44.5 inches
Wal-Mart 5T 38.5 - 42 lbs 42 - 44.5 inches
Zutano 4T 36 - 40 lbs 39 - 42 inches
janie and jack 5 40 - 44 lbs 44 - 52 inches
tea 6/M 46 - 51 lbs 45 - 48 inches
vineyard vines 4T 36 - 40 lbs 39 - 42 inches