Late teens. I started gaining some weight in my mid-20s so they've gotten a little bigger. Also I take evening primrose oil for PMS which I think has helped them along (EP oil is known for increasing breast size). I've always been an A but am more like a B now because some of my A bras are a little on the tight spot. I'm so proud of how far my lil weezils have come. Oh yeah, during PMS days for the past year or so they swell to gargantuan size and ache like the dickens. I've always wanted bigger boobs but not like that.