There is no age-chart for breast size.
It just depends on how big the girls breasts are, I am a girl and I started to wear one at the age of 8 and now I am 11.
There is not a specific breast size that a girl "should" be. It is all in your genetics. That is why some girls are more than qualified to work at Hooters and other girls cannot even fit into an A cup. There are 13 year olds that have bigger breasts than 20 and 30 year old women. Your breast size for you age is what it should be, whatever size you are. You just have to be you!
I think that a 16 year old girl's breast areola size should be around a size 16
breast size should be 36 and stomach size should be 24 and bump should be 36
I am a 16 year old girl and I wear the bra size 34AA and when I was 13 my breasts did not even start growing and I did not have a training bra when I was 13. You should talk to your mom or a doctor cause your bra size is not normal for your age.
There are some females fully grown with same size or even bigger.
Are you sure about this because a 13 year olds breasts would look like a womans breasts
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38c
A 12-year old girl should wear a size 12/14. If the girl is tall, she may want to go up a size so things will fit better.
There is no average since each girl/woman is different and breast size is based on DNA.