it is more correct to compare with the height:
(Unit：CM)
120=4T-5T：Top length=50 bust=88 sleeve=12 Pants length=40 waist=46,fits for: 110-120cm height / 4-5 Years Old

130=6T：Top length=52 bust=92 sleeve=13 Pants length=43 waist=48,fits for: 120-130cm height / 6 Years Old

140=7T-8T：Top length=54 bust=96 sleeve=14 Pants length=46 waist=50,fits for: 130-140cm height / 7-8 Years Old

150=9T-10T：Top length=56 bust=100 sleeve=15 Pants length=49 waist=52,fits for: 140-150cm height / 9-10 Years Old

160=11T-12T：Top length=58 bust=104 sleeve=16 Pants length=52 waist=54,fits for: 150-155cm height / 11-12 Years Old

170=13T-14T：Top length=60 bust=108 sleeve=17 Pants length=55 waist=56,fits for: 155-160cm 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.