Have a look at iasenkos thread and especially his calculator. It's well written and explains the system plus gives you an easy tool so that you can calculate the earliest time when you could rank up (depending on your forum activity and "value"):
| ________________ | _____________________ | ________________ |
| RANK | Activity | Merit |
| Brand new | 0 | 0 |
| Newbie | 1 | 0 |
| Jr Member | 30 | 0 |
| Member | 60 | 10 |
| Full Member | 120 | 100 |
| Sr. Member | 240 | 250 |
| Hero Member | 480 | 500 |
Legendary -
Random in the range | 775-1030 | 1000 |
Easy calculating your Activity based on your registration day.