Related Questions:

How does 50% extra xp weekend stack with other bonuses?

Extra experience from equipment

What is the formula for additional experience on items?

How does "Increases bonus experience" on items work?

While there is some good information in the answers to the above questions, I feel none of them give the complete picture.

In Diablo 3, there are a number of different ways to increase your exp gain. Assuming your level is fixed (at 70, most likely), we have the following effects:

  • "Strength in Numbers" buff (group bonus)
  • "Increases bonus experience by ..%" from equipment and/or ruby in head slot
  • "Monster kills grant +... experience" from equipment and/or Gem of Ease
  • Difficulty bonus (a % bonus)

These all modify the base experience received from slaying a monster (again, assuming for simplicity that player level isn't taken into account). For simplicity, I will refer to them as (in the same order).

  • Group%
  • Bonus%
  • Bonus
  • Difficulty%

Now, how these work on their own is pretty straightforward, but how do they stack when two or more are present? Knowing the exact way they stack could make a big difference when evaluating different item properties.

For example, having "Monster kills grant +... experience" on a few pieces of gear could make a big difference if the calculation is something like:

Net gain = (Base + Bonus) * Group% * Bonus% * Difficulty%

However, it would be almost useless at higher difficulties if the formula was more like:

Net gain = Base * Group% * Bonus% * Difficulty% + Bonus

The names aren't very descriptive, but if I had to guess, my guess would be something like:

Net gain = (Base + Bonus) * (Bonus% + Difficulty%) * Group%

However, this is mostly guesswork. Is there any official source (or someone doing a bunch of science) that clears this up? I also remember someone saying there was a difference in how experience gain was calculated in Greater Rifts compared to the rest of the game. Any truth to this?

(Note: When multiplying by X%, I naturally mean multiplication by 1.00 + 0.01*X. Multiplying by (X% + Y%) refers to a multiplication by 1.00 + 0.01*(X + Y))

Edit: While broad in scope, the question primarily applies to the current (as of August 2015) state of the game. So patch 2.2.1 primarily (which also applies to season 4/patch 2.3.0, since there are no changes to the exp formula planned, only base exp balancing and bonus exp being averaged over the party).

  • Good question, I might suggest making a note of what patch you're using, I'm not sure if XP calculations have changed in recent updates. Your question doesn't seem patch specific, but its answer might be.
    – Dpeif
    Aug 12 '15 at 20:39
  • @Dpeif Good point. For my purposes it obviously applies to the latest patch (as of now), but it might be good for future reference.
    – Svj0hn
    Aug 12 '15 at 21:37

Data from this post suggests that Bonus% is a separate multiplier in Greater Rifts, rather than additive with game difficulty. I've seen multiple people say that Bonus% is additive with game difficulty outside of Greater rifts, but I'll restrict the rest of this post to GR.

As you mentioned, Bonus% is (sum of all experience gear across the party)/(number of party members), since experience gear is divided evenly across the party in 2.3.

With perfect rolls on Leoric's Crown and Ring (note this gets 45% at level 70, not 35% as the post mentions), you're looking at (82+30+45+20+50)/4 = 56.75% bonus exp per exp-geared char in a 4-man party.

In his runs, adding one exp person brought exp up 63.95% from ~8.6M to ~14.1M. Adding two exp people brought exp up 73.84% (per exp-geared person, 147.65% total) from ~8.6M to ~21.3M. He only ran 10 runs in each test set, and rifts vary widely, though it could be he forgot to mention other changes in the gear, such as additional rubies in helms of non-exp chars or using Gem of Ease on the measured character.

Patch 2.1.2 brought the change:

The "Monster Kills grant X experience" affix is now multiplied by game difficulty

All of this leads me to believe that this is the correct formula for Greater Rifts:

Net gain in GR = (Base + Bonus) * Group% * Bonus% * Difficulty%

I've seen reports that it's different for outside of Greater Rifts, which changed in Season 2 or 3, but it wasn't in patch notes.

As for how useful the +Bonus is, I think they've purposely scaled Base such that it is extreme at low levels and barely noticeable at high levels. If the percentage discrepancies above are due to Gem of Ease, you're talking about a 5-16% exp difference, which is worth it.

Also I believe experience shrine is a multiplier as well, but my sources for this are outdated, so it could have changed.

  • Excellent answer! However, an increase from 8.6 to 21.3 is around 148%, not 74%. So one of the numbers (21.3 or 73.84) seem wrong.
    – Svj0hn
    Aug 20 '15 at 6:26
  • 148% for 2 people = 74% per exp-geared person. I'll update to clarify
    – pfayze
    Aug 20 '15 at 16:35
  • Thanks. The first post you linked seem to be exclusively testing in greater rifts. I remember greater rifts scaling differently to normal play some patches back, and I wonder if this is still the case. I suppose I could easily test it by killing the same mob with and without Bonus% gear in T6.
    – Svj0hn
    Aug 24 '15 at 7:11
  • When I look at my increased xp gain it seems to make very little difference. Ex on t1 you get 300% increased xp gain, then with a ruby +35%, so the total is just 335%. Not 405%, which is what you might expect. With such little improvement I don't understand why anyone on hc uses xp gem instead of life.
    – MrFox
    Sep 17 '15 at 7:34
  • 1
    @MrFox as mentioned in my post, "Bonus% is additive with game difficulty outside of Greater rifts". So in T1, you get 335%, but in GR10 (equivalent of T1), you get 405%. So in HC, most people likely use life outside of GR and xp in GR, at least when they're a support build and exp farming rather than pushing higher ranks. Also xp being multiplicative in GRs was a bug that they decided to leave in because it incentivized GR over normal rifts. The character sheet xp number used to display the intended number rather than actual. I'm not sure if that's fixed yet.
    – pfayze
    Sep 21 '15 at 3:18

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