it is more correct to compare with the height:(Unit：CM)80=9M-12M：length=42 bust=70 sleeve=34, fits for: 65-75cm height / 9-12 Months90=18M-24M：length=45 bust=74 sleeve=37, fits for: 75-85cm height / 18-24 Months100=3T：length=48 bust=78 sleeve=39, fits for: 85-95cm height / 3 Years old110=4T：length=51 bust=80 sleeve=41, fits for: 95-105cm height / 4 Years old120=5T：length=54 bust=82 sleeve=43, fits for: 105-115cm height / 5 Years oldNote:1.There is 2-3% difference according to manual measurement.(1 inch = 2.54 cm)2.All measurement in cm, please note 1cm=0.3937ch, 1 inch=2.540cm3.Please check the figures carefully and order the right size, don't completely depend on the " age advice". It's just for reference.