it is more correct to compare with the height:
Unit: CM
L=2T：length=41 bust=62 sleeve=30; fits for: 75-85cm height / 2 Years Old

XL=3T：length=43 bust=65 sleeve=31; fits for:85-95cm height / 3 Years Old

XXL=4T：length=45 bust=68 sleeve=32; fits for: 95-105cm height / 4 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.