it is more correct to compare with the height:
(Unit：CM)
110=4T：length=67 waist=22 hips=34, fits for: 95-105cm height / 4 Years Old

120=5T：length=71 waist=23 hips=36, fits for: 105-115cm height / 5 Years Old

130=6T：length=76 waist=24 hips=38, fits for: 115-125cm height / 6 Years Old

140=7T-8T：length=80 waist=25 hips=40, fits for: 125-135cm height / 7-8 Years Old

150=9T-10T：length=84 waist=26 hips=42, fits for: 135-145cm height / 9-10 Years Old

160=11T-12T：length=89 waist=27 hips=44, fits for: 145-155cm height / 11-12 Years Old

170=13T-14T：length=94 waist=28 hips=46, 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.