it is more correct to compare with the height: (Unit:CM) 120=5T:length=56 hips=35, fits for: 110-120cm height / 5 Years Old 130=6T:length=60 hips=37, fits for: 120-130cm height / 6 Years Old 140=7T-8T:length=65 hips=39, fits for: 130-140cm height / 7-8 Years Old 150=9T-10T:length=69 hips=42, fits for: 140-150cm height / 9-10 Years Old 160=11T-12T:length=74 hips=44, fits for: 150-160cm height / 11-12 Years Old 170=13T-14T:length=76 hips=46, 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.