.
You have good breasts.
You do.
They're the only ones you get and they're awesome.
And anybody who says any different better leave NOW.
OK. Are we clear?
Your boobs = great.
Now I've got the crazy harangue out of the way, lets talk a little bit about sizing and measurements. To get your measurements you're going to need...
For step one:A tape measure.
A mirror.
(optional) a good chum or your sweetie
A bra that you feel comfortable in (not padded or lift-uppy though)
For step two:The shop with the largest selection of underwear (in your price range) in town.
Step One.You'll need to whip your shirt off. You can leave everything else on. Though I once had a lady strip completely nekkid. She was mortified when I asked if maybe she'd maybe like to put her pants back on... so yep. You can leave your drawers on.
Now you need to run your tape measure under your boobs. Under where your bra band is sitting. If you need to lift the girls up to do this, do. But keep your arms neutral otherwise. You need to keep your tape measure as straight as possible here (this is where a mirror or a good chum come in handy). Like this (but with YOUR arm down) :

So. My number here is 35, which means that I round UP to 36 (odd numbers always round up to even ones). I actually feel a bit weird and cringey posting my numbers like this. But I am going to suck it up. BECAUSE... It's just a number. It can't hurt me and it doesn't say anything about me other than the bra size I wear. And it's kind of important not to fudge here, no holding your breath and yanking the tape measure. It's the path to no fun-ness. I
KNOW this because as a size 42 who couldn't psychologically let myself be anything but a 38 I was really uncomfortable and shopping for new bras was a BRUTAL exercise in self-loathing (sound too dramatic? You should (not) try it.)
Ok. So you have your band measurement. Awesome, because from here on out everything gets ARBITRARY.
and I really can't be emphatic enough about this. Completely ARBITRARY.
Measuring with a tape measure is half-assed-MAYBE-this-will-give-you-a-clue AT BEST. So with that in mind here's where you measure.

Got a number?
Now the (totally arbitrary) way to figure out your cup size is to work out the difference between your band measurement and your breast measurement. And every inch that your boob measurement is larger than your band measurement is a cup size.

On me this measurement is so wrong as to be laughable. My band size is 36" and my breast measurement is 41".So I should be a DD cup. Which would be awesome. but I'm NOT. I wear a B/C cup depending on where I am cycle-wise. A few things can throw this measurement off. A round back (like mine), weight on your armpits (yup, I got that too), broad shoulders, hell, pretty much anything.
So the key is to move on to....
Step Two.Hit up the lingerie section.
Now what I used to do is bring a woman the same bra in a few different cup sizes. Then we'd start with the smallest and work our way up until we got the fit correct. Also note that depending on your breast shape you should try a few different styles of bra. Balcony bras work better on a small, high rack. And a plunge style works well on a bigger boob, or if your fullness rides to the side.
The first thing you need to do is adjust the straps on the bra you're trying on. Not too loose is the key here BUT the straps shouldn't be gouging your flesh (owwie) and you should be able to jam your fingers t'ween your strap and your shoulder.
Once you've got the bra on the first thing you need to do is make sure you're IN it. Which means
leaning forward a bit. Sticking your hand into your bra between your boob and your bra on the outside, (armpit side) and hoicking the girls forward, then shaking em' like a showgirl.
Now. How are we doing?
1. About that band size; is the band laying horizontal or is it hiking UP at the back? If it's hiking then you need to go down a band size.
2. Where are your underwires? If you lift your arms up and have a look at where your boobs start and your armpits finish, THAT'S where your underwires (or the edge of the cup) should be sitting. The wires (or cup edge) should be laying completely flat to your body all the way around your boob. If they're not then you go up a cup size.
3. How about yer pits? The cup shouldn't be tanglin' with your armpits at all, but if you carry extra flesh there (me! me! I do!) then you need to be careful that you're shaking into your cup properly. Nobody needs their bra to give them another set of under-armpit boobs.
4. Whats going on up top? Are you muffin-topping over the cup? Up a cup size. Are there wrinkles? Down a cup size. Neither working for you? Then try a different
style.
So to recap, your perfect fit should be level on the band (the band does most of the support work) it should be smooth on the cup, not muffin-topping anywhere and not wrinkled. Any kind of pinching or horribleness anywhere is a deal breaker..
And lastly if at all possible your underwear should make you feel like "woo! I got's my pretty drawers on today!" which is not to say that sensible is a bad thing; but if you put on a bra and it's super comfortable but you find it so ugly you die a little inside then you need to take it off and keep looking. The
Oh well, nobody will see it rule does not apply here. YOU will see it and you're somebody.
Ok. So this post was the length of a novel. And kind of bossy. Good job if you made it all to the way to the end here!
Hit me up in the comments or send me an 'mail if you have any questions.
X
P.S. If you're looking for a nursing or maternity bra then there's a thing I wrote about that right
here.
The chart of arbitrary numbers is from here.