Why do bras slip off shoulders?

Bras slip off shoulders primarily due to a band that's too loose, which destabilizes the entire fit and forces straps to migrate outward where they're prone to sliding. When the band lacks proper support, the strap anchor points sit wider on your back, pushing straps toward the shoulder edge where they can't maintain their grip.

Strap placement and back design also play significant roles, with wide-set strap anchors (common in balconette styles) creating more slip than center-pull or racerback designs that keep straps closer to your neck.

Your shoulder anatomy matters too; narrow or sloped shoulders increase slip risk, which is why convertible straps with racerback capability can be transformative for maintaining a secure fit.

Additionally, stretched-out elastic from wear and improper laundering (especially heat exposure) compromises strap tension, making them unable to hold their position throughout the day.