As far as I can tell, it's something like this:

damage reduction = armor / (armor + 100)

Is this accurate?

2 Answers 2


Yes, that's correct. The calculations are:

Armour Resist: Damage Reduction = Total Armor / (100 + Total Armor)

Magic Resist: Damage Reduction = Total Magic Resistance / (100 + Total Magic Resistance)

  • 1
    And despite what it might seem, Armor does not have diminishing returns. Commented Aug 16, 2010 at 22:36
  • @Raven: That's true, but it's important to remember that a lot of armor is not better than a mix of armor/hp. Because armor boosts your survivability by a percentage of your hp, and most hp items give a flat hp boost, it's often better to buy hp once you have significant armor. I'm sure you already know this, I'm just leaving it here for any other readers.
    – Matthew
    Commented Aug 19, 2010 at 17:04
  • @Raven Dreamer I would love for you to explain how Armor doesn't have diminishing returns. As is clearly stated in the formula, it does have diminishing returns. A diminishing return means that the more armor you add the less damage is reduced for each point of armor. Commented Nov 3, 2010 at 19:47
  • @Steven Oxley -- you're looking at it from the wrong perspective. While the amount of armor required per point of %damage reduction does increase (the diminishing returns you're seeing), the effectiveness per point of armor doesn't decrease. I'd open a new question if you'd like to know more -- comments aren't really suited to the indepth explanation a fuller answer would require. Please don't condescendingly assume I don't know what "Diminishing Returns" mean. Commented Nov 3, 2010 at 19:54
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    @Raven Dreamer gaming.stackexchange.com/questions/10244/… Explain away. I didn't mean to be condescending. I was just making sure we had a definition of "Diminishing Returns" to work off of. Commented Nov 4, 2010 at 16:24

When it comes to reduction It is indeed diminishing, but when You work out the formula for Ehp (Estimated hp) 1 point of armor actually always gives 1 additional % of hp based on the base hp.

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    EHP is 'effective HP', i.e. the amount of damage you can soak up.
    – Catalept
    Commented Jun 12, 2012 at 3:45

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