[2019] How does physical damage reduction work exactly?

Originally posted by golgol12

I am pretty sure that armor and other souces of reduced physical damage multiply with each other.

But, you know what, I am now questioning myself. /u/mark_ggg please help. Does armor stack multiplicative, or additive with other sources of "additional Physical Damage Reduction"? I always thought the damage gets reduced by armor first, then the remainder of that passed to phys damage reduction.

Originally posted by Saint_Yin

Just so you know, you can mitigate the damage by more than 90%. The 90% cap is only on the first step, here are the other ones:

Physical Damage reduction: This stat is gained from armor and sources which state "additional physical damage reduction." These apply additively with each other, up to a cap of 90%. It applies to raw physical damage taken.

Physical damage reduction sources are as follows:

• Endurance Charges (4% per, up to 12 with 3 base, 3 from tree, 1 from ascendancy, 1 from Shaper 2H weapon, 2 from rings, and 2 from corrupted Death's Door boots)

• Basalt Flask (15%, affected by flask effect)

• Gorgon's Gaze (5% while moving)

• The Red Trail (10% while stationary)

• Disintegrator (1% per Shaper/Elder item, up to 9)

• Tree (Soul of Steel: 5%, Singular Focus: 4% while channeling, Duelist node: 4% while affected by Guard skill)

• Ascendancy (Juggernaut: 1% per endurance charge, Guardian/Ascendant: 1% per aura, Necromancer: 1% per zombie)

• Chaos Golem (5% at 22, can be boosted with golem effect)

• Major Pantheon deities (Solaris: 6% if no more than 1 nearby enemy, Lunaris: 1% per nearby enemy, up to 8)

• Minor Pantheon deities (Tukohama: 2% per second stationary, up to 8%, Gruthkul: 1% per hit taken recently, up to 5%)

Physical Damage taken from attacks: This stat is gained from some equipment, and applies after armor, but before reduced/less sources. Not sure why, because flat damage reduced is monumentally more valuable if it's lopped off the last step, and it's not like this -X damage stat is too strong.

There is only one notable example of this:

• Immortal Flesh: -40 to -50 physical damage taken from attacks.

Reduced Physical Damage taken: This is applies after Physical damage taken, but before Less. This does not have a cap, so if you find a way to get 100% reduced physical damage taken, you're immune to physical damage regardless of armor.

Here is a list of various effects that fall into this category:

• Fortify (20% reduced, up to 60% increased effect in tree)

• Unshattered Will (20% reduced)

• Unbreakable (Jugg, 5% reduced)

• Bloodletting (Passive skill, 5% reduced if enemy is bleeding)

• Silent Steps (Passive skill, 5% reduced if enemy is blinded)

• Conqueror (Champ, 6% reduced if enemy is taunted)

• Brutal Fervour (Slayer, 6% reduced if leeching)

• Born in the Shadows (Sabo, 10% reduced if enemy is blinded)

• Ghost Shrouds (Trickster, up to 9% reduced)

• Weave the Arcane (Trickster, 6% if 200 mana spent in last 4 seconds)

• Frigid Wake (Occultist, 10% reduced from hits if enemy is chilled and "nearby")

There are more, but the most notable inclusions are tied to elemental damage or damage over time, both of which are not relevant to the OP's question.

Less Damage taken: This applies after all other steps, and applies multiplicatively with itself. This means Less sources can never fully reduce damage and sees diminishing returns as more sources are applied.

Examples of this include:

• Arctic Armor (13% less)

• Infused Channeling (8% less if supporting a channeling skill with the Physical tag)

Edit: Added some more to the list of reduced damage taken, due to a couple responses splitting hairs.