it is more correct to compare with the height:
(Unit：CM)
S/120=5T/6T：length=70 bust=91 shoulder=35.5 sleeve=40, fits for: 110-120cm height / 5-6 Years Old

M/130=7T/8T：length=74 bust=95 shoulder=36.5 sleeve=44, fits for: 120-130cm height / 7-8 Years Old

L/140=9T/10T：length=78 bust=99 shoulder=37.5 sleeve=48, fits for: 130-140cm height / 9-10 Years Old

XL/150=11T/12T：length=82 bust=103 shoulder=38.5 sleeve=52, fits for: 140-150cm height / 11-12 Years Old

XXL/160=13T：length=86 bust=107 shoulder=39.5 sleeve=56, fits for: 150-160cm height / 12-13 Years Old

XXXL/170=14T：length=90 bust=111 shoulder=40.5 sleeve=60, fits for: 160-165cm height / 13-14 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.