it is more correct to compare with the height:
Unit: CM
120=5T：length=60 bust=78 Sleeve=43; fits for:110-120cm height / 5 Years Old

130=6T：length=63 bust=82 Sleeve=45; fits for:120-130cm height / 6 Years Old

140=7T-8T：length=66 bust=86 Sleeve=47; fits for:130-140cm height / 7-8 Years Old

150=9T-10T：length=69 bust=90 Sleeve =49; fits for:140-150cm height / 9-10 Years Old

160=11T-12T：length=72 bust=94 Sleeve =52; fits for:150-160cm height / 11-12 Years Old
Note:
1.There is 2-3cm 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".