[Doll]

Honestly, your underbust measurement is basically your band size. I know it seems really tiny, but there's reason behind that. By using a band that is about the size of your underbust, it puts all the pressure on the band, not the straps, so not only does the band not move around all day long and your bra doesn't need constant readjusting, but it also prevents the back pain associated with all the weight being on the straps. Also, if you can immediately hook a bra on the tightest hook when trying it on, it's too big. You need one that you can barely hook on the loosest one; that way, over time, as the bra stretches, you can keep it at the proper tightness and continue to wear it properly for much longer.

I understand bras now O_O. Thank you.

LOL
That's actually the exact same information that finally made me understand them.