Anonymous wrote:I'm a 30 E.
You should measure under your breasts around your ribcage. Some like to use that exact measurement for a band size, most will add about 4 inches to that for their band size. Using the exact measurement usually feels way too snug. I added 3 inches to mine and my bras are very comfortable on the loosest hook while still fitting properly, barely even feel like I'm wearing a bra. (27 inch ribcage, opted for 30 band size instead of 28)
Then, measure around your boobs, all the way to the "most sticking out" point (usually around the nips). If your saggy or deflated, have someone help you or use a counter or something to make your boobs stick up and out like they are supposed to if they had more tissue.
The difference between them is how you determine the cup size. There are some charts online that show this. I think the Breakout Bras site has one.
If you go down in band size, you go up in cup size and vice versa. (If I went for a 28 it would have been 28F)
To the OP, I would make sure your fitted properly and then try on different brands to find one that is comfortable for you. Definitely look for wider straps and a bra with at least 3 hook closures on the band. This will give you better support.
One of the PPs here. This is interesting because this is NOT AT ALL how I was measured at Nordstrom.