PSA: a lot of people wear the wrong size of bra for them, let alone the wrong TYPE of bra/cup/underwire length for their breast tissue and appropriate lift/separation.
Save yourself the discomfort and either try and size yourself at home with a tape measure, or book a fitting at a store (if they're not free then don't go to them, that would be absurd). It's worth it to actually be comfortable in something that you wear all of the time and have to spend money on.
Some of you may be wondering "underwire LENGTH?? That's an issue??" And the answer is YES. It all depends on breast tissue and your body type; if you have firm or soft breast tissue, as well as the amount of it, AND how it hangs on your body, AND the shape of your sternum.
If your underwire is too short/sits too low on your sternum and you have heavy breasts, it's not going to be nearly as good support as a longer underwire that sits higher on your sternum.
@GoblinHellion Is important.
Sex & The City even did a little scene around it at one point, which I always felt was a bit of a PSA slid under the radar (when honestly, that show could've just had the girls talk about it openly).
Hanan! 🌻
Kale 
Noted Pervert 🧄