it is more correct to compare with the height: Unit：CM 100=3T：length=58 bust=56 fits for: 100-110cm height / 3 Years Old
110=4T：length=62 bust=59 fits for: 105-115cm height / 4 Years Old
120=5T：length=66 bust=62 fits for: 115-125cm height / 5 Years Old
130=6T：length=70 bust=65 fits for: 120-130cm height / 6 Years Old
140=7T/8T：length=74 bust=68 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.