Experience Points

Experience points (also exp, rep or XP) are the primary reward for undertaking adventures in Borderlands. Every character starts with 0 experience points and level 1. Completing missions and killing hostile creatures results in experience points awarded to all of the characters present in the group. Completing achievements or challenges will increase the experience point total of the character for whom the achievement or challenge was completed.

Once the experience is gained your character will increase his/her level upon reaching a certain threshold. The maximum level cap for all character is currently 50, but the experience points are still awarded.

Level improvements

For each level gained your character will receive 15 extra health points added to the 100 base, which means the health calculation is: 100 + (level-1)*15. Also, every level acquired rewards your character with 1 skill point starting at level 5 meaning a total of 46 skill points at level 50. Other characteristics like melee damage or resistance also increase at higher levels.
edit Notes

* As each level is gained a graphic text pop up will overlay the screen with the words "Level Up". At this point health and shield capacity become fully charged at their new level and the character's action skill is also recharged.
* Experience points can be gained during the course of the game, and can only be lost by exiting the game without saving. Should an unsaved exit occur, the experience total will be reverted back to the most recent game save.
* Many gamers have found faster ways of leveling up, such as inviting low level player to game that involve higher level characters which leads to higher level enemies and eventually much quicker way of leveling up. This practice is often referred to as "power leveling".
* The amount of points needed for a specific level can be calculated using the formula: f(x)=60*(x^2.8-1), with x denoting the level and rounding to the next integer (e. g. 3788.1 becomes 3789). This formula is correct for all levels except level 45. For this level the deviation between the formula and the given experience points is 59.

Level - XP required
1 - 0
2 - 358
3 - 1,241
4 - 2,850
5 - 5,376
6 - 8,997
7 - 13,886
8 - 20,208
9 - 28,126
10 - 37,798
11 - 49,377
12 - 63,016
13 - 78,861
14 - 97,061
15 - 117,757
16 - 141,092
17 - 167,207
18 - 196,238
19 - 228,322
20 - 263,595
21 - 302,190
22 - 344,238
23 - 389,873
24 - 439,222
25 - 492,414
26 - 549,578
27 - 610,840
28 - 676,325
29 - 746,158
30 - 820,463
31 - 899,363
32 - 982,980
33 - 1,071,436
34 - 1,164,850
35 - 1,263,343
36 - 1,367,034
37 - 1,476,041
38 - 1,590,483
39 - 1,710,476
40 - 1,836,137
41 - 1,967,582
42 - 2,104,926
43 - 2,248,285
44 - 2,397,772
45 - 2,553,561
46 - 2,715,586
47 - 2,884,139
48 - 3,059,273
49 - 3,241,098
50 - 3,429,728