That the sizes on all of our bras is a scam. So, what should we all do to make sure we're getting the support we need? Go natural. Thank you, stephen. Abc's bianna golodryga -- that's what I do. --... See More
That the sizes on all of our bras is a scam. So, what should we all do to make sure we're getting the support we need? Go natural. Thank you, stephen. Abc's bianna golodryga -- that's what I do. -- Has the story. A bra this sheer, when you're belt like me? I'll try it. But I don't see how it supports. Reporter: If your bra is anything like your life, one expert says, you probably need more support than you're getting. This is a 28a. Reporter: What size is this? This is a 46m. Reporter: Meet linda becker, the bra lady. She's dedicated her life to being supportive and on a mission. Becker says eight out of every ten women are wearing the wrong bra size and don't even know it. I realize that all of the companies, about ten years ago, changed all of the sizes. You know, they wanted you to think that your back was smaller and your breasts were bigger. Reporter: What once was a 36d is now a 32g. How can you make sure to get the right fit? They should be halfway between your elbow and your shoulder. If you look in the mirror and you're lower than that, your bra is too loose. Reporter: We asked volunteers to get fitted by our expert. Look before and after. Becker's advice, get fitted by a professional. She says it's a good idea to replace your bras every six months. To lengen the life of your bra, start by using the loosest hook. Then, tighten it over time. There's no need to wash between each use. You can wear a bra seven or eight times before cleaning it. If your bra isn't right, it doesn't feel good. Reporter: Proof, becker says, that beauty may be skin-deep. But when it comes to support, that's priceless. For "good morning america," bianna golodryga, abc news, new york.
This transcript has been automatically generated and may not be 100% accurate.