When people talk about breast size, they often describe it in terms of bra size. Pinning down an exact number for what's “normal” or "average".
Breast volume and bra sizes by country: USA leading by far!.
That's a tricky question to answer, because it depends on a few factors such as age and whether we're talking natural, pre-surgery sizes only.
We polled 1, Americans and 1, Europeans to discover women's (and men's) ideal breast size and then compared this to average breast sizes in Europe.