I was trying to calculate the relative differences of a few pieces of gear - namely ones that add +damage% to one damage type, and I couldn't figure out how all these damage types are applied.

For the sake of argument, take a barbarian with the following:

  • 9,000% increased damage from strength.
  • 40% increase to physical damage
  • 25% increase to primary skill damage (Simplicity's Strength gem)
  • +15% damage to some primary attack (Bash, let's say)

and afterwards, what happens if he has 400% critical strike damage and he gets a critical strike? Are all of these sources multiplicative?


The basic answer to this question lies here, at Diablo 3 Reaper of Souls Guide: Damage Formula Explained. In summary, certain types of multipliers are added together, and then all multipliers are multiplied together.

The basic rule is that everything is multiplied together. Most factors start at 100%, and have multipliers added on. For example, +40% physical damage results in a 1.4 multiplier, and +20% primary skill damage results in a 1.2 multiplier when using that skill. Note that some multipliers are added together before the final calculation. For example, elemental damage, native weapon damage, and skill damage modifiers are added together to a base 100%.

So, to give numbers to the pieces you've included: (90 * Weapon Damage) * 1.4 * (1 + 0.25 + 0.15). When you get a critical, which will occur, on average, according to your critical hit chance, then the 400% damage is multiplied in as 5 (base 100% + 400% additional). So, if your weapon's minimum damage is 100, your total minimum damage would be 17,640. On a critical, your minimum damage would be 88,200 for that hit.

Note that other factors are in play in terms of your "character sheet" damage, such as the speed factor (so, your character sheet damage is balanced to give an average damage per second value). Doing this allows you to compare slower and faster weapons fairly, because you'll see the actual raw output from each weapon in a comparable fashion.

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  • Does elemental damage%+ have a cap? I have 4 items all with Fire dmg +[17-20%], so, from the link I assume they all add up? – David Yell Aug 10 '15 at 9:19
  • As far as I can tell, and from what I remember of the game, all elemental damage is combined. I don't think I've ever observed a cap. – phyrfox Aug 10 '15 at 15:43
  • Yep, according to d3planner.com they do stack. i.imgur.com/SVXr3Yx.png – David Yell Aug 11 '15 at 9:15

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