That deppends on what size you are. If you measure right under your bubes you can tell part of your size. The other part will be either aaa, aa, a, b, c, or d. Thos are the most common sizes but, they do go bigger.
there is no aaa. the smallest is 28aa.
what is the bra size of your mother at the age of 15,that is the size
There is no particular size for 15 year old girl's to wear. Every girl is different in size and therefore you should get measured. If you go into shops like Debenhams or La Senza, they will measure your size for free and make sure you are wearing the correct size of bra. i think any size will do if it works for ex) i know a 12 year old size c and another 20 size b
Bra size is not based on age, but on measurement of the body.
Get yourself fitted.
If you don't know what bra size you are you should ask your mum if you can go and get your breast measured and fitted to an appropriate bra.
You can call your girlfriend and ask for her bra size. If you aren't comfortable asking her, then buy her something that is not a bra.
If your bra makes it hard to breath in, you should wear a larger band size bra. If your boobs don't fit in the cups of your bra, you should wear a larger cup size.
You could measure it. if there are tags on the bra that tell you, then look for it.
you can get a bra measure from primark