By the team at XA.net‘s count, from Facebook’s own figures, about 495,362,600 users. Still a lot, perhaps the other 4.6mm or so are from other countries than the 186 listed, or people who live on the moon or whatever. Here’s the data in an excel sheet, along with country populations from Wikipedia for all to use as they wish (but please keep attribution intact).

Here’s the top 25 – Southeast Asia has made a big push:

Here is the full data file in Excel. Enjoy!