What is the process behind the Democratic Iowa Caucus?

I've been trying to figure out exactly how the Democratic Caucus in Iowa works for days, but I can't seem to find any sources that lays it all out entirely. I know that there were thousands of delegates that were chosen yesterday, and that these will vote on a county level and then a congressional district level until 48 national delegates are chosen. The part I'm really confused about is how do the votes in precincts convert into the first round of delegates. But I could really do with a complete explanation about how the entire process works, to be honest.

• While a perfectly valid question, this seems to be relatively easily answered via google. I'd start with the wikipedia article on it: en.wikipedia.org/wiki/Iowa_caucuses#Democratic_Party_process
– user1530
Feb 3, 2016 at 4:53
• Yes, I've read this. But it's very vague and doesn't go into the details. It barely says anything about the higher level elections. For example, it doesn't say what the difference between a state and district level convention is. How are the districts determined? These are the kinds of things that aren't explained anywhere I've looked. Feb 15, 2016 at 5:08

Several political scientists published a book called "Why Iowa?" which described these processes in depth. Much of the book is available online for free.

Chapter 3 describes "caucus math" and how delegates are assigned based on precinct results. Delegates are assigned proportionally based on the number who caucus for that candidate in each district, with rounding:

If in a group of 200 caucusgoers there are 110 for Obama, 50 for Edwards, and 40 for Clinton once all alignments are made, then Obama will be allocated 55% of that precinct’s county convention delegates, Edwards 25%, and Clinton 20%. (pg.57)

The caucusgoers elect the individual delegates from among themselves.