Looking for a guide to shot sizes

[Devonai]

I must admit my ignorance to the specifics of most shot sizes. Can anyone point me to a guide that indicates diameter of shot or average number of pellets per round?

For instance, I know that 000 buck is .36 caliber and 00 buck is .33 thanks to Federal's box guide. What about T, B, or BB? How many pellets, on average, in a 2 3/4 #4 birdshot shell?

Thanks in advance.

 

[Red Label]

Most of the power manufacturers have a ton of info on their websites. Here is my favorite http://www.hodgdon.com/data/shotshel/tabchart.php

I hope I did this right. If not just go to Hodgdon.com and go into their shotshell data. Its got everything you are asking for