Millions of people are finally figuring out their true bra size thanks to a TikTok trend that made an online sizing tool so popular it crashed twice.
TikTok users first had an inkling they weren't getting their bra size right when lingerie educator Madison Alexandra shared a video explaining how two very different looking breasts could actually be the same size.
"A breast that is rooted to the chest wall over a small surface area will appear more projected," she explained in the video which has amazed 4.4 million views.
"It can therefore appear larger than a breast of the exact same volume that attaches to the chest wall over a larger surface area."
Alexandra says cup size is measured by volume, not visual perception, while two sets of breasts may be the same size the wider set breasts will appear more shallow.
She uses a stocking filled with rice as a visual example and at the end of the video urges viewers to visit the online bra size calculator called 'A Bra That Fits'.
TikTok user @charisse_v took Alexandra's advice, and in a response video explains she used the calculator to figure out her correct bra size.
Charisse usually wears a 34A or B but says the underwire digs into her breast tissue. Upon throwing her measurements into the sizing calculator she was stunned it suggested a 32D or 32DD.
"Ok let's try this on there's no way," she says to viewers as she buys her new bra.
She was surprised the 32D fit perfectly and in a later video found a 32DD fit even better. Though her breasts looked to be the same size, the larger bra was wider in the cup allowing for a more comfortable fit.
Charisse's video has been viewed 12.5 million times, receiving 1.7 million likes from people who also decided to jump onto the A Bra That Fits website and figure out their own sizes.
The calculator was so popular it crashed twice.
"Does everyone need to be doing this right this second? The website won't load," one frustrated TikTok user commented on Charisse's video.
The A Bra That Fits calculator requires six measurements while regular bra sizing techniques only measure the underbust and use an outdated calculation to figure out the cup size.
The calculator also asks what gender people were assigned at birth to account for differences in sizing for non-binary and transgender people.
While the Reddit A Bra That Fits community has championed this way of sizing since 2010 it's receiving a new flood of support due to the millions of people directed there from TikTok.
A new SubReddit guide has been created for those new to the community.