The technique used by bra-fitters and corsetiers to approximate breast size and therefore bra size. Often men and women can learn this technique for their own common use.
Customer: Hi there, I would like a bra fitting please
Jennifer: OK, well I breastimate you are a 10/32C so lets start there shall we?
Daniel: Woah look at her GIANT breasts!
Beth: Sorry man, shes just wearing the wrong bra and theyre hanging out. I breastimate she's only a 14/34 C.