I found this online... and I don't know how accurate it is but it makes sense.  Keep in mind the numbers count from when you join a roster... so your overall stats are not an accurate indicator of where you are...   

How to get each rank:

• Rank 1: Noob or you leave games early!
• Rank 2: Play 14 games or win 9 (whichever comes first)
• Rank 3: Play 27 games or win 17
• Rank 4: Play 54 games or win 34
• Rank 5: Play 108 games or win 68
• Rank 6: Play 216 games or win 136
• Rank 7: Play 432 games or win 272
• Rank 8: Play 864 games or win 544
• Rank 9: Play 1728 games or win 1088
• Rank 10: Play 3456 games or win 2176

Here's a link to the site... http://www.socombattles.org/confrontationranking.htm