As I play more Diablo 4, the relationship between Armor and Damage Reduction confuses me more. So, I did a few research on Armor and Damage Reduction, and would like to share my findings. Knowing this, you won’t be wasting Diablo 4 Gold on unnecessary gear.
There are 3 sections in this guide:
- Basic Damage Reduction Formula with Armor and Resistance
- Armor Damage Reduction Deep Dive (Armor Efficiency, Armor vs Higher Level Enemy & % Armor Mechanism)
- What do I do with this knowledge?
The armor mechanism is complicated and dynamic. The aim of this guide is to give you a high level idea on the relationship between Armor and Damage Reduction and offer the necessary tools for you to find out the specific gains in your specific situations.
Basic Damage Reduction Formula With Armor And Resistance
Let’s first start with the background, the basic formula. There are two main cases, Physical Damage and Non-Physical Damage.
For Physical Damage, let’s say an enemy’s attack is 100 Physical Damage. I am Lv87 and have 6557 Armor. This gives me 60% Damage Reduction from the same level enemy. So, let’s assume the enemy is the same level for now. I will then take 100 x (1 - 60%) = 40 Damage.
For non-Physical Damage, let’s say an enemy’s attack is 100 Lightning Damage. Armor will contribute to Damage Reduction to half of the Total Damage while Resistance contributes to the other half. So, it will be 100 x 50% x 60% = 30 Damage Reduction from Armor.
Let’s say I have 40% Lightning Resistance. In World Tier 4, Monsters’ attack overcomes 40% Resistance. So, it will be 40 x (1 - 40%) = 24% Lightning Resistance. Then, Resistance will contribute to 100 x 50% x 24% = 12 Damage Reduction from Resistance.
In total, I have 30 (from Armor) + 12 (from Resistance) = 42 Damage Reduction. And I will take 100 - 42 = 58 Lightning Damage Armor Efficiency.
Armor Efficiency
Now that we know the basic formula, I’d like to dive into why my 6557 Armor equals to 60% Damage Reduction. This section contains lots of and lots of numbers. Skip to the last section if you are only interested in the conclusions and the best practices.
Diablo 4 Dev shared a few examples on Armor to Damage Reduction in their Livestream from the 1st Screenshot, per unit Armor to Damage Reduction Efficiency decreases as players level up. Also, it seems that for a specific Level, per unit Armor to Damage Reduction is constant.
For example, at Lv 88, the Damage Reduction per armor is around 0.018%. I did some local testings and found out it is partially true. I swapped gears on and off on my Lv88 Sorcerer and recorded the following Armor to Damage Reduction Data Points. Then, I calculated the differences between Armor and Damage Reduction at each stage and got the per Armor Damage Reduction.
So, the trend is that as Armor goes up, the Damage Reduction per Armor goes up, too. I assume what Dev shared is the Cap of the Damage Reduction Per Armor. Which in this case, it is approaching 0.018% gradually.
Also, one important note is that this Damage Reduction is more powerful than it looks.
Let’s pick 2 data points from the 1st graph. I have 5284 Armor that leads to 41% Damage Reduction and 5817 Armor that leads to 48% Damage Reduction. This 5817 - 5284 = 533 Armor difference leads to 7% Damage Reduction.
But the actual Damage Reduction is 11.9%. Because let’s say the damage is 100. In the 5200 Armor case, we are taking 100 x (1 - 41%) = 59 damage. And in the 5800 Armor case, we are taking 100 x (1 - 48%) = 52 damage. Relatively, we are taking 52 / 59 = 88.1% of the previous damage. That leads to 1 - 88.1% = 11.9% Actual Damage Reduction.
So, I calculated each stage for Actual Damage Reduction. It also goes up as Armor goes up, to a point of 3.5X efficient or more.
One extra note is that for the first 3 rows, I took some Armor down to just collect data points. But they are not the common cases. The last 4 rows are the common cases where I have all gear equipped but swapping with % Armor Stats or not.
To make it easier to understand, I made 2 common cases: one is Skull 250 Armor, the other is 10% Armor stat from gear, which usually leads to 500 Armor.
And we can see on average, 250 Armor is roughly 6% Actual Damage Reduction 500 Armor is roughly 14% Actual Damage Reduction.
One thing to note is that all the Damage Reduction I mentioned above are Physical Damage Reduction.
For Non-Physical Damage Reduction, I will skip the calculation steps and put the results here. Assuming the All Resistance is 35%. In World Tier 4, that is going to be 21%. In common case, roughly the actual Non-Physical Damage Reduction for 250 Armor is 3% and for 500 Armor is 7%. The higher the Armor or the Resistance, the higher the Actual Non-Physical Damage Reduction is.
Armor VS Higher Level Enemy
Now, we have an idea on how 6557 Armor leads to 60% Damage Reduction at Lv88. And Diablo 4 Dev also shared a graph on how Higher Level Enemy makes Armor less efficient. I checked what the Dev mentioned in the Livestream and here are the keys.
First, Armor Damage Reduction Caps at 85%. So, the first flat line doesn’t mean enemies within 17 levels higher than the player. Do not depreciate the Armor Efficiency. But the 2000 Armor is too much at Lv1 that a Lv17 enemy starts to depreciate the Armor Efficiency enough that the value hits below 85%.
Second, when first looking at this graph, I am not sure whether the Armor Efficiency Depreciation is dynamic to the level difference between the Attacker and the Player.
For example, if I am Lv1, a Lv88 enemy would treat my 2000 Armor as 7% Damage Reduction from this graph. What if I am Lv50 or Lv88? Will the 2000 Armor be treated as some other value from a Lv88 Attacker?
So, I checked the Livestream more closely and the Dev explicitly mentioned that “Usually players can acquire 2000 Armor at around Lv30” “If the Lv30 Character fight a Lv100 Monster, the 2000 Armor can only absorb 5%”. This means that the Armor Depreciation is only related to the Attacker Level, not to the Level difference.
After doing a local testing that I tried to get around 2000 Armor for my Lv88 character, it says 7% too here. This confirms that the Armor Depreciation is only related to the Attacker Level. This also explains that why Armor Efficiency drops as Player level up from the screenshot earlier. Because Attacker levels up, too.
So it is a kind of designed to be always hungry for more Armor to better survive as players level up. That there won’t be a point that Armor is enough to hit 85% damage reduction cap because of the ultimately 54 levels of higher enemies in Nightmare Dungeons.
Percent Armor Mechanism
Now,we understand what Armor means to both the same level and higher-level enemies. But how can we acquire more Armor?
There are two types of Armor Source. One is the base armor. It comes from Gears, Strength and Elixir or Incense. The other is % Armor, it comes from Stats on Gears or Aspects like Disobedience.
After doing some testing on % Armor, I find it is additive, meaning that if I have 4800 Armor and 20% Armor. And if I get another 10% Armor, it will be 4000 x (1 + 20% + 10%) = 5200 Armor instead of 4800 x (1 + 10%) = 5280 Armor.
Does that mean stacking % Armor is bad? No. As I mentioned earlier, Armor Efficiency gets higher as Armor grows. And for Actual Damage Reduction, it can grow as much as 3.5X efficiency. Plus, it makes all Armor from Elixir or Incense even more effective.
To give you an example, I have around 6600 Armor and around 30 % Armor. Once I use a 900 Armor Elixir, my Armor goes to 7800, which is another 1200 difference and the Actual Damage Reduction is 1 - (1 - 80%) / (1 - 62%) = 47%. So, this 900 Armor means I am going to take only half of the Physical Damage. Isn’t that insane?
So, you may wonder, how would the Disobedience % Armor work with this? I find it is additive to the current % Armor And to my gears, its Actual Damage Reduction is as crazy as 69%! Imagine how effective it is to combine the 900 Armor Elixir and Disobedience!
Also Read: How To Calculate Damage Increases In Diablo 4? - Damage & Defense Mechanics Explained
Conclusions And Best Practices
What can I benefit from this Armor Deep Dive?
So to recap, for Lv85+, we can roughly treat
250 Armor (Skull) as
- 6% Actual Physical Damage Reduction
- 3% Actual Non-Physical Damage Reduction
500 Armor or 10% Armor as
- 14% Actual Physical Damage Reduction
- 7% Actual Non-Physical Damage Reduction
1200 Armor as
- 47% Actual Physical Damage Reduction
2200 Armor from Disobedience as
- 70% Actual Physical Damage Reduction
- When it has 100 stacks
The lower Level,
- The higher the Actual Damage Reduction per Armor is
For example, 300 Armor is roughly 10% Actual Physical Damage Reduction at Lv75. We can start comparing the % Armor stat with other Damage Reduction Stats. When compared to Conditional Damage Reduction, like from Burning/Close/Distant Enemy, % Armor is worse when the condition is met. When compared to % Damage Reduction, % Armor is better since the majority damage is Physical Damage.
Also, as Armor Damage Reduction Efficiency greatly increases (to 3.5x or more) as Armor goes up, the more Armor, the better. This means the Item Power of defensive gears matters. The 200 Armor on Paragon Board from the Burning Board matters. And the Armor from Elixir plays a great role in Survivability.
And all these get multiplied by % Armor from Gear Stats Try to collect as many % Armor stats as possible on your Helm/Chest/Pants/Amulet I was able to use this knowledge to switch my gears to decently survive in Tier 66 Nightmare Dungeon and beat it as a Level 85 Lightning Sorcerer.
