At age 13 how big should your breasts be?

Every girls breast are different. The size usually runs in the family. If your family members have larger breasts then you will most likely have larger ones too. Breasts start to develop when puberty hits. Puberty can start between the ages of 11 to 16 some times earlier sometimes later. If you have small breasts now, they could grow bigger. Don't think there is something wrong with you if you have small breast at your age or any age. everyone is different.