I really wish lingerie companies would put their models in the right size bras :/

Honestly if your underwire is sitting forward of your armpit, you're wearing too small a cup. If your band can be pulled out far away from your back, you're wearing too big a band. Your breast tissue extends under your armpit and round to your sides, cradle it.

If your bra is uncomfortable or leaves marks, you're wearing the wrong size and possibly style. Your bra shouldn't be lifting when you raise your arms - your band is too loose.

Don't get measured in a high street shop. They add 4" to your band. This isn't needed and will put you in the wrong size. If you get measured in a high street store, go down two band size from whatever measurement they give you and go UP two cup sizes.

The average cup size in the UK at least is about a 34C. This is wrong! Most of these people have 4" added to their ribcage measurement. They're actually a 30DD. The last time I got measured by a so called professional, they put me in a 34D. My ribcage under my breasts is 26".

Why do I need an extra 8" of band? Because shops don't stock 26" bands as standard. They don't even stock 28" bands with any cup size over maybe a C. To properly measure your chest, get a tape measure, measure your ribcage under your breasts SNUGLY but making sure you can still

take a good breath where your band sits. Then measure around the fullest part of your chest standing straight (this isn't always aroudn your nipples). Make sure the tape measure is level all around your chest. If you have someone who can help, great. Dont pull the tape tight.

Now you're gonna take that measurement again but whilst bending at a 90° angle from the hips. Add those two measurements together and divide by two. If you've got a half measurement, round up to the next full number. Now however many inches difference between your band and bust

Thats your cup size. Its one inch per cup. If you've got a 6" difference, you're an E cup (this is for UK sizes, I know US has DDD). Oh and this method works perfectly for trans women too.