Leveling and Experience

Every monster type has a base experience per difficulty (monstats.txt Exp), multiplied by a value for its level (monlvl.txt); see monster level for where that level comes from. What you get of that depends on the difference between its level and yours, and from level 70 on the game cuts all experience further.

A monster's level decides its experience, its life and damage, and the item level of what it drops. Where that level comes from depends on the difficulty:

• In Normal every monster has its own level (monstats.txt Level). levels.txt gives Normal areas an area level too, but monsters keep their own, so one area can hold monsters of different levels.
• In Nightmare and Hell monsters take the level of the area they spawn in (levels.txt MonLvlEx). So the same monster has a different level in every area it spawns in.
• Champions are 2 levels higher, uniques and their minions 3 (super uniques too), in every difficulty.
• Act bosses have a fixed level per difficulty, whatever the area level: Andariel is 75 in Hell.
• An item drops with the level of the monster that dropped it as its item level.

Source: The Arreat Summit, Monster Bonuses and the game files.

Monsters close to your level give full experience. Under level 25 the experience falls off both ways, for monsters more than 5 levels above or below you. From level 25 a monster above you gives its experience times your level divided by its level, so a level 30 character gets 30/40 = 75% from a level 40 monster; monsters below you fall off the same way as before.

From level 70 every kill gives less, wherever you are (experience.txt ExpRatio), on top of the level difference. At level 85 you get a quarter of the experience, at level 98 less than 1%.

• Monsters give more experience with more players in the game: experience × (players + 1) ÷ 2, so 2 players give 1.5×, 8 players 4.5×.
• In a party, a kill gives 35% more when a party member is in the same area. It is split between the party members within 2 screens of the kill, by their level: each gets their level divided by the sum of their levels.
• Dying in Nightmare costs 5%, in Hell 10% of the experience needed for your next level. You never lose a level, and you get 75% of it back by picking up your corpse where you died.

Source: The Arreat Summit, Experience.

The best area for every 5 character levels from level 6 to 70, in Normal and Nightmare (the levels before come by themselves in the starting areas): the most experience per kill times the area's monster density, among the areas whose monsters are at most 5 levels above you. It counts every monster type once, for one player, and leaves out how fast you clear an area, so take it as a guide. The graph of each area shows how much experience you get there per character level, to see how long you can stay. In Hell, terror zones beat any fixed area.

It only counts the areas a regular, self-played character has reached by then, from the character levels below. These are a rough guide: a few levels under where each act's monsters start, as you enter an act a little behind. The Secret Cow Level opens after killing Baal.