But 80B is just good for me!

Of course it can be, that it is good for you. We have very different shapes, different body structure. For example a girl who trains a lot (professional swimmer) will definitely need different bra than a girl who sits in front of the computer all her day – even if the measurement shows the same size.

The point is, in my experience the A/B/C sizes are rare (still, if it’s really what you need, there is nothing wrong about it). Very rare. I’m aware, that if you say  80% of woman is wearing the wrong size, all of them will be convinced, that they are in this lucky 20%. I know, because I was :)

You may say: “But my current 80B is not too loose! How can it be wrong?”

Let's imagine a person with 75/92 below/in size. 80B is (more or less, I'm simplifying it) for a person with 85/92. It will not fall down, because it is supported by your bust (it is actually squeezing the soft tissue of your bust).

75B is for a person with 70/87. Of course it will be too tight. You won't be able to wear it! Even 75C will be more too small.

But try 70F. It's made for a person ~75/92. It should be just ok (because it will stretch). You won't feel it, the same way you don't feel your panties. The band will support the bra (and it was not at all in 80B). This way you will even feel less load on the strips.

You don’t believe, that the band so tight will be comfortable for you? Do an experiment! Try it: here are the instructions.

My advice is: measure yourself. When you are in the shop try the size recommended by the calculator. If they don’t have your band/cup, you may try another one, but follow the rule: if you take the band 5cm bigger, you have to take the cup two letters smaller. If the band is 5cm smaller – the cup goes up by 2. E.g.: if you are recommended 65G and you don’t see any 65-band bras, try 70E.

Important: try only soft bra. Not pushups and not the ones with the 5mm layer of sponge – even if they are so cute. Those kind of bras simply cover your breast and give it their shape. What the bra should do is to support your bust and just slightly shape it.

The size is not a cure for everything. The perfect bra must have the shape of cups and the shape of underwire that fit. There are no parameters on the lingerie tag, that will tell you anything about it. You must try it.

And I eventually found a nice website with explanation, what does a “good bra” mean.