Why do bras roll up?

Bras roll up due to a combination of factors like support, fit, and construction.

The most common culprit is a band that's too loose. Since the band provides 80-90% of a bra's support, a loose band migrates upward while the front sinks, creating that frustrating ride-up effect that leaves you constantly readjusting. 

Cups that are too small or shallow push the entire frame away from your body, encouraging the bottom edge to curl and the back to climb, while overtightened straps compound the problem by pulling the back band upward instead of providing balanced support.

Additionally, bras without adequate structural elements like wide wings, stabilized cradles, or flexible boning may not be up to the task of staying in place when faced with heavy breasts or extensive moment. Even well-fitted bras can develop rolling issues over time as elastic fibers lose their recovery through wear and improper care, particularly exposure to heat from dryers, which is why rotating your bras and air-drying them helps maintain their supportive integrity.