I would say depending if they are of average weight, a B or C cup. The more they weigh they larger their cup size will be.
I am a 11 year old girl and I have no boobs. So really the average size is none. I only have breast buds.
34 b
36 D
32A or 34A would be average bra size for a 12 year old girl.
34B
b or c
There is no average since each girl/woman is different and breast size is based on DNA.
1 cm
The average size is a 32 A or 34 A but if you are bigger or smaller its just how your body is growing
The average bra size for teenage girls can vary widely, but it is generally around A to C cup sizes. It's important to remember that bra size can change frequently during the teenage years due to growth and development.
Everybody is totally and completely different.
AAA