Level 87

Total Experience Required 4,403,270

Level 100 progress: 64.51%

This is roughly the same as:

Killing 14,678 people in Warzone, or...
Killing 14,978 people in Execution, or...
Killing 12,439 people in Wingman, or...
Scoring 3,145,193 points in Guardian, or...
Scoring 9,572,327 points in Annex, or...
Scoring 5,793,777 points in Submission.

Horde (TU4)

Completing 22,017 waves on Casual, or...
Completing 14,678 waves on Normal, or...
Completing 11,009 waves on Hardcore, or...
Completing 8,807 waves on Insane.

Or a combination of the above. Have fun!