Breast spillage: If the bra cup is cutting into your breast tissue or your boobs are popping out from under the bottom of the cup, you probably need to size up.
The gore isn't sitting flush: The front center gore, which is the front center part of the bra band, should lie flat against the skin. If there’s a lot of space, that’s a sign you’re in the wrong size.
The band is riding up: If your bra band is riding up your back, this is a good indication that the bra you're wearing is too small.
The bra is leaving red marks and hurts to wear: Your bra should never be uncomfortable. Even though it may be common to see some red marks lingering on your skin after you take off your bra, this shouldn't be happening if you're wearing your correct size and your bra is properly fitted to your body.