it is more correct to compare with the height:
Unit: CM
90=2T：length=40 bust=68 sleeve=32; fits for: 75-85cm height / 2 Years Old

100=3T：length=42 bust=70 sleeve=34; fits for: 85-95cm height / 3 Years Old

110=4T：length=44 bust=72 sleeve=36; fits for: 95-105cm height / 4 Years Old

120=5T：length=46 bust=74 sleeve=38; fits for: 105-115cm height / 5 Years Old

130=6T：length=48 bust=76 sleeve=40; fits for: 115-125cm height / 6 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.