How to Check Whether a Tight Bra Band or Small Cup Causes the Problem
Fasten the bra backward and upside down so the cups do not pull on the band. If the band becomes comfortable, the cups probably need more volume or depth. If the band still feels uncomfortably tight, compare a roomier sister size.
How to Tell a Wrong Bra Cup Size from a Cup Shape Mismatch
Empty space does not always mean the cup is too large, and overflow does not always disappear by adding volume. Notice where the mismatch appears: at the neckline, wire, cup bottom or center. A different cup height, wire width or depth may solve a localized problem more effectively than another size.
Use the bra style finder to compare constructions after confirming the band and cup volume are reasonable.
When to Stop a Bra Fit Test Because of Pain or Skin Irritation
Firm support should not cause sharp pain, numbness, broken skin or restricted breathing. Remove a bra that causes these symptoms. Persistent breast, rib or skin symptoms need advice from an appropriate healthcare professional rather than a sizing tool.