This is based on the American average height of 3-13 year old girls.
SIZE:3-4Years: Tail Length 39"--Hips/Waist 20.5"/ 15.8"---Bust 23" Recommended Age: 3-4years
SIZE:5-6Years: Tail Length 41"--Hips/Waist 21.7"/ 16.5"---Bust 23.6" Recommended Age: 4-5years
SIZE:7-8Years: : Tail Length 43"--Hips/Waist 22.9"/ 17.7"---Bust 25" Recommended Age: 6-7years
SIZE:9-10Years: : Tail Length 45"--Hips/Waist 24.5"/ 18.5"---Bust 26" Recommended Age: 8-9years
SIZE:10-13Years: Tail Length 47"--Hips/Waist 26.0"/ 19.3"---Bust 27" Recommended Age: 10-13years
NOTE:The model is 7 Years old girl, height49", 52LBS, fits for SIZE:7-8Years.