A sports bra should fit snugly to provide proper support, but not so tight that it feels uncomfortable or restricts movement. The band, which provides most of the support, should be firm and lie flat around your ribcage without riding up or digging in. You should be able to fit two fingers comfortably between the band and your skin. The straps should be secure without slipping off your shoulders or digging in, and the cups should fully contain your breasts without any overflow or gaping. A good fit will minimize bounce, offer stability, and allow you to move freely during your workout. If you experience any discomfort, try adjusting the straps or trying a different size.