Experience Points

Experience Points (or XP for short) are a measurement of character progress. The player character can earn experience points for killing creatures and solving quests. They are used to determine when a character should gain a new level. Different amounts of experience points are awarded for killing more dangerous creatures. For example, in Fallout 3, killing a deathclaw nets 50 experience points while killing a radroach gives only 1. Experience points can also be gained for disarming mines and traps, picking locks, hacking computers, passing speech challenges, doing sections of a quest and, in Fallout: New Vegas, completing challenges like killing a set amount of an enemy. The number of experience points earned for an accomplishment are not dependent on character level.

Fallout
XP in Fallout is a conventional type similar to Dungeons and Dragons where levels are separated by a large amount of experience. For example, it takes 1,000 XP to reach level 2, 3,000 for level 3, 6,000 for level 4, and so on.

Fallout 2
Fallout 2's XP system is similar to Fallout's. The only major difference is that leveling requires more XP than in Fallout.

Fallout 3 difficulty modifier
Changing the difficulty level will also change the experience gained from killing enemies. Playing on Very Hard instead of Normal makes a kill worth 50% more experience, while playing on Very Easy makes it worth 50% less. For example, a deathclaw is worth 25 XP on Very Easy, 50 XP on Normal and 75 XP on Very Hard.

The additional experience from fights on Very Hard compared to Very Easy is somewhat compensated by the enemies being much tougher. In the end, the player's skills and play style determine which difficulty setting allows for optimal leveling.

XP caps at level 20 on all difficulties without the Broken Steel add-on, which increases the cap to level 30.

Fallout: New Vegas
Fallout: New Vegas does not reward XP based on the level of difficulty selected, despite the manual (PC and X360 version) stating otherwise. This somewhat alleviates the stress encountered while playing the game simultaneously on Hardcore, as it is not necessary to play it on Very Hard.

Unlike Fallout 3, Fallout: New Vegas awards XP for kills made by followers. This increases the usefulness of followers and significantly reduces the hassle of having to compete with them for XP.

Fallout 4
The higher the Sole Survivor's Intelligence, the more experience points they earn.

The Idiot Savant perk offers significant XP increases, increasing the XP gained from any action by 3x or 5x depending on the perk rank. The higher the Intelligence, the lower the chance of activating the perk.

Similar to Fallout: New Vegas, Fallout 4 also awards experience points for kills made by a follower. However, the player character must damage the target for at least 25% of its Hit Points before the follower makes the kill in order for the experience points to count. XP is also awarded for enemies that kill each other within sight of the player character. In Survival mode, enemies that are killed by the Sole Survivor yield twice as much experience. This is the first time since Fallout 3 where a higher difficulty means more experience gain.

Outside of increasing Intelligence, there are perks and consumables that increase the number of experience points the player character earns.


 * Permanent


 * Temporary


 * The sleeping perks and Quiet Reflection do not stack with each other.

Fallout 76
Experience points (XP) are gained from completing a wide variety of tasks, such as defeating enemies in combat, crafting items or completing quests. There are multiple ways to increase XP gain:
 * Each point of Intelligence (INT) grants +2.072% XP.
 * Buffs:
 * (Well) Rested: Resting in a bed for a while grants +5% XP for a varying amount of time depending on bed used and the presence of an ally.
 * The Path to Enlightenment: After completing the event, interacting with the Wise Mothman will grant +5% XP for 1 hour.
 * Strong meat sweats: Contributing 15 prime meat during Grahm's Meat Cook will grant +5% XP for 15 minutes.
 * Picking up the Zeta Invaders or Atomic Command magazine will grant +1 INT for 1 hour.
 * Public teams:
 * Casual team: +1/2/3/4 INT per member and time spent in the team
 * Daily Ops team: +25/50/75/100% XP from Daily Ops completion, per member and time spent in the team
 * Events team: +25/50/75/100% XP from event completion, per member and time spent in the team
 * Hunting team: +25/50/75/100% XP from legendary enemy kills, per member and time spent in the team
 * Perks:
 * Inspirational (Fallout 76) (Charisma): +5/10/15% XP, when playing in a team
 * Night Person (Perception): +1/2/3 INT, during the night
 * Mutations:
 * Egg Head: +6 INT (+7.5 with Strange in Numbers)
 * Herd Mentality: +2 INT (+2.5 with Strange in Numbers)
 * Marsupial's Penalty to INT (-4) can be suppressed for 1 hour by consuming the serum, or reduced to -1 with Class Freak level 3.
 * Apparel:
 * Unyielding legendary armor: +3 INT per part (+15 total)
 * Intelligence legendary armor: +1 INT per part (+5 total)
 * Internal database power armor helmet mod: +2 INT
 * Underarmor with shielded casual lining: +3 INT
 * Aid:
 * Buffs can be increased with the appropriate perks and mutations (the latter increased further in tandem with Strange in Numbers)

Fallout Tactics
XP in Fallout Tactics are given to all party members, regardless of the number of members. The game does not feature difficulty modifiers; however the Tough Guy game mode can provide 100% XP bonus (30% in versions prior to 1.27).

Fallout Shelter
Experience in Fallout Shelter exist on a per-dweller basis, rather than there being an experience total for the player.

There are various methods of yielding experience for dwellers:
 * Successfully rushing a room that the dweller is working in
 * Being in the room when enemies are killed (either during quests or incidents)
 * Over time, all dwellers that are not ready to level up and are working in production room will slowly gain experience

Bugs

 * Earning experience points and dying or loading an older save right before they register yields the points in the older save.
 * This appears to only be a display issue as the points are not added to the total on either platforms, this is easily realized if the player would have gone up a level.
 * It is possible to earn XP past where a level-up should happen without the game registering the level-up. This results in being stuck at level one. The XP counter may end up reading something like 600/200, indicating that a level-up should have happened 400 XP "ago". This may happen at any level or only from the start of the game. If it happens at the start of the game, beginning a new game fixes this bug, so watching the XP meter closely is a good idea.
 * Upon starting a new character, the game will recognize the level 1 character as a continuation of the most recent save (typically a level 30 character). This will make the player unable to level up at some point. This can be fixed by deleting all the save files and starting a new game.
 * This can also be solved by following these steps:
 * Start a new game on a different profile that has no save file from the game.
 * Go to memory under system settings and delete the most recent auto save from the bugged profile.
 * Start a new game, and the bug should not occur. If it does, try the same process but exit the town before 200 XP is reached.
 * If a single accomplishment results in enough experience to level up twice, the game will register two level-ups but will not award additional skill points. E.g., if the 1000 XP for completing the quest "Ring-a-Ding-Ding!" would result in going from level 6 to level 8, the skill points that would result from attaining level 7 are lost.
 * Fixed in a recent patch.