If happen to know a busty and thin lady close enough, you've probably heard her complain about how hard is to find bras that fit.

There are two ( actually more ) reasons for this:

The first one is easy to understand. It is hard to find the size, no store sells bras over a D cup in a less than a 36 band. Stores don't focus on that market because they assume it's not profitable, lets just cater to the masses (with less boob mass).

Now, here's the fun part

The second reason is a tad less obvious. The cup sizes on smaller bands increase at a bigger threshold than in bigger band sizes. Now why is this?

One inch represents 1/32th (3,125%) parts of a 32" band size, and that same one inch represents 1/40th (2,5%) of a 40" band size.

As the band size goes up, the inch difference that determines cup sizes becomes relatively smaller ( 1/32 is 25% bigger than 1/40 ).

How is that a sizing problem?

This means that cup sizes in smaller bands are going up faster than in bigger bands. This means there are less "in between" sizes.

With the previous example in the 32 and 40 bras, since the cups go up 25% faster in the smaller band, every 5 cups increase in the 40 band you only get 4 cup changes in the 32 bra.

It's like bigger band sizes have small, medium and large options, and smaller sizes have only small and large options .