Any part of the breast would hang over a hand placed immediately beneath the breast
Upper bound:
The breast's volume is less than the volume of a sphere with the same diameter as the character's facial area
If this seems large for 'medium' breasts, just remember:
Breasts in anime art defy biology, physics, and common sense. [...] these tags don't make sense when you try to apply them to living people. They're made for two-dimensional teenage heroines for whom anything less than double-Ds is on the small side. - iridescent slime
