Certain bra brands, and certain bra models within a brand (and sometimes even a bra model in just a certain colour) have cups that are either bigger or smaller than standard. This is especially frustrating when you buy online. The world still lacks standarised bra sizes,
The page has two lists: one of small cupped bras, and one of big cupped bras. Apart from the cup size, there are useful details such as an unusually tight / stretchy band, very narrow or very broad underwires, and much much more ! The page also includes detailed instructions about adjusting the calculations of the bra size, if for example the bra you want to buy is big-cupped but has a very stretchy band !
The information is based on the forums Lobby Biusciastych and Lobby Malobiusciastych, amazing goldmines of bra wisdom from hundreds of girls wearing correct bra sizes !
The brands I have listed are all high quality, affordable, and most offer a very wide range of sizes. The list might be a bit Europe-centric, but on the other hand most of the world apart from the UK has quite a poor selection of sizes. On info about how to buy these bras online, read this.
In my workshop: a table of narrow and broad underwire bras, as well as a list of models with very stretchy or very tight bands !