it is more correct to compare with the height:
(Unit：CM)
7/90=2T： length=54 bust=58 sleeve=34, fits for: 80-90cm height / 2 Years Old

9/100=3T： length=59 bust=61 sleeve=37, fits for: 90-100cm height / 3 Years Old

11/110=4T：length=64 bust=64 sleeve=40, fits for: 100-110cm height / 4 Years Old

13/120=5T：length=69 bust=67 sleeve=43, fits for: 110-120cm height / 5 Years Old

15/130=6T： length=74 bust=70 sleeve=46, fits for: 120-130cm height / 6 Years Old

17/140=7T-8T： length=79 bust=73 sleeve=49, fits for: 130-140cm height / 7-8 Years Old
Note:
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=2.540cm
3.Please check the figures carefully and order the right size, don't completely depend on the " age advice". It's just for reference.