Show Shirt sizes?

So I'm wondering how to measure myself for a English show shirt? I'm not sure how to do it.
Also I can't try them on at a tack store because they are not carried regularly, they have to be ordered in due to space problems in the stores(all are small).

Also does anyone know the conversion charts for sizes? Like what would a 16 be when the sizes go up from 30 etc. (Just picked random numbers).

Generally you go up one size from your bra size. So if you wear a 34 something you'd order a size 36 shirt. But remember that different brands are cut differently. My favorites are Essex, which tend to be pretty fitted. If you're bigger chested (which I'm definitely not!) you might want to go up another size. IMO Ariats are very boxy and I could almost go down a size. Tailored Sportsmans have a different sizing altogether. Closer to your typical dress size.

I would be about a size 12/14...large/xlarge shirt depending on the type of tshirt...and I had to get a 42 for it to fit around my neck. Even then, it is still pretty snug. It does fit around my chest quite well with some room, and I am a 36DD. The shirt is Sterling Collection by RJ Classics, and I bought it from Equestrian Factory Outlet (Canadian store).

Just as a reference, the jacket I have is a 14R, by RJ Classics.

Thanks Guys! I now have some ideas on what to look for.

I have to say that your tiltle sounds like a tounge twister! LOL

I never even thought about that till I read your comment! But it's so true!