Calculate the points you need to advance a certain percentage:
The following table shows how many GCW points you need to earn each week to progress from a certain rank to the next rank in a certain number of weeks. The idea is from nebaf's GCW FAQ.
Rank  1 Week  2 Weeks  3 Weeks  4 Weeks  5 Weeks 
Private  10000  3333  1999  1428  1111  Lance Corporal  19285  3970  2211  1534  1173  Corporal  21666  4062  2240  1547  1181  Sergeant  38333  4423  2345  1597  1210  Master Sergeant  54999  4583  2389  1617  1222  Sergeant Major  104999  4772  2440  1640  1235  Lieutnant  Impossible  16222  9484  8116  7525  Captain  Impossible  21546  10251  8640  7997  Major  Impossible  37166  10829  9018  8406  Lieutnant Colonel  Impossible  287080  11240  9139  8725  Colonel  Impossible  Impossible  15851  10746  10109 
Theoretical rank progress caps (theoretical means it is the mathematical limit but you wont be able to reach it due to diminishing returns) and GCW points needed to reach a certain percentage of these caps:
Rank  Progress Cap (rank total)  Progress Cap (%)  GCW for 50%  GCW for 80%  GCW for 90%  GCW for 95%  GCW for 98% 
Private  10000  200  10000  40000  90000  189999  489999  Lance Corporal  6750  135  6750  27000  60750  128050  330749  Corporal  6500  130  6500  26000  58500  123499  318499  Sergeant  5750  115  5750  23000  51750  109050  281749  Master Sergeant  5500  110  5500  22000  49500  104499  269499  Sergeant Major  5250  105  5250  21000  47250  99550  257249  Lieutnant  3409.5  68.19  9645  21455  52208  1081956  Impossible  Captain  3152.28571428571  63.0457142857143  9825  22335  57750  658852  Impossible  Major  2885  57.7  9680  22039  57616  350763  Impossible  Lieutnant Colonel  2611.8  52.236  9269  21851  55758  189970  Impossible  Colonel  2354  47.08  10479  24169  51363  106344  267186  General  2083.66666666667  41.6733333333333  15000  30217  49116  70263  93906 
