When it comes to determining girls' jeans size, you can use two different methods:
1. Determine jeans size based waist measurement and inseam measurement:This method is most accurate.
Measure around the natural waistline: The waist is usually just above the belly button (narrowest part of torso). Still not sure where the waist is? Stand in front of a mirror, and bend to one side. The waistline is simply where you can see a natural indentation in torso on this side. Take a relaxed measurement, and keep the measuring tape parallel with the floor.
To find inseam measurement, measure from crotch to ankle (or measure from crotch seam to leg end if you already got a pair of jeans that fit perfect). See illustration above. Use the measurements to determine jenas size in the size chart below.
2. Determine jeans size based on girl's age: Determine jeans size from size chart below based on age. Easy-to-use method, but it is not very accurate.