Level 58

Total Experience Required 1,048,332

Level 100 progress: 15.36%

This is roughly the same as:

Killing 1,748 people in Warzone, or...
Killing 1,783 people in Execution, or...
Killing 1,481 people in Wingman, or...
Scoring 374,405 points in Guardian, or...
Scoring 1,139,492 points in Annex, or...
Scoring 689,693 points in Submission.

Horde (TU4)

Completing 2,621 waves on Casual, or...
Completing 1,748 waves on Normal, or...
Completing 1,311 waves on Hardcore, or...
Completing 1,049 waves on Insane.

Or a combination of the above. Have fun!