Diablo 3 Game Mechanics Complete Guide

Diablo 3 Game Mechanics Complete Guide by Rhaloz

Base Mechanics


Armor reduces all incoming damage by a certain percentage. Armor can be increased by items with armor and the attribute strength. Every point of strength gives one point of armor. Skills and spell can increase the total amount of armor too.

%damage reduction = [Armor/(Armor+Clvl*50)]*100      Clvl= Character lvl

The Clvl is not the lvl of the player but the lvl of the monster attacking you. This is important as the may monster lvl in act 4 inferno is lvl 65.

Armor against  Lvl 60 monster


Resistance against X

Resistance against one element reduces the damage of the element by a certain percentage. Resistance can be increased by items with +Resistance against X and the attribute intelligence. Every point intelligence increases resistance by 0.1. The damage reduction follows the same math as armor but with different absolut numbers. Resistance and armor work multiplicative.

%damage reduction = [Resistance/(Resistance+Clvl*5)]*100   Clvl= Character lvl

The Clvl is not the lvl of the player but the lvl of the monster attacking you. This is important as the max monster lvl in act 4 inferno is lvl 65.


Dodge is a percentage chance to avoid all damage of an an attack. You can dodge melee, ranged and magical missile. It was stated that ground based (area) attacks can also be dodged (need confirmation). Dodge increases through dexterity.

DEX to dodge:
0 – 100 gives 0.1%
100 – 500 gives 0.025%
500 – 1000 gives 0.02%
1000 – 8000 gives 0.01%

Summed up:
100 dex–>10%
500 dex–>20%

Skills can increase dodge. Different sources of dodge do get multiplied for total dodge.

Example: 200 dex ->12,5% dodge ; Mantra of evasion: 15%
Together: 0.875*0.85=0.74375 hit chance –> ~25.6% dodge

Shield Block

Shields hold three basic stats. Armor, block chance and block amount.

Armor is added to your armor mitigation. Every melee and ranged attack has the block chance to be blocked up to the block amount  of damage. If the attack holds more damage as the shield can block the additional damage will hit you. The block test happens after the damage reduction through armor and other sources. High armor works very good with blocking. Because of this it is a very good defense option for barbarian.

Total Damage Reduction

For Information or comparing different builds and setups it is often useful to calculate the total damage reduction of your character. Different sources of damage reduction are added multiplicative. Be aware to only use defense mechanics that work against the damage typ/ attack typ you are interested in. This total damage reduction is a median over time as effects as block or dodge are random events.

Basic Formula:

drx= Source of damage reduction

The barbarian Hoggar has 70% armor mitigation, a shield with 20% block and 10% dodge through dexterity. As a barbarian he also gains 30% damage reduction against every source.

Compared to physical melee damage:
With the assumption that the full damage can be blocked with the shield we see that Hoggar gets only 15% damage from physical melee attacks.

Compared to magic damage dot:
Hoggar is not well prepared to fight magic damage and only achieves 79% damage reduction. He gets ~40% more damage from magic dots than from melee strikes.

Attack Speed

Attack Speed in diablo 3 is normally presented as “Attacks per second”. The faster your weapon is the more attacks per second can be achieved. This does directly affect skills and spells.

Direct hit attacks like Bash have a shorter animation and can be used faster.

Damage over Time effects like Rend “tick” more often and produce more damage. The absolut time of the skill does not change.

Channeled skills like Whirlwind or Ray of Frost “tick” more often and produce more damage. This does also increase the amount of resources the spell needs as it becomes “faster”.

If your character uses two one handed weapon he gets a unique attack speed bonus of 15%.

There are two main categories for attack speed. One is the modified weapon speed. The base weapon speed increased by all speed increasing affixes on the weapon. The second is the sum of all other attack speed increasing factors, even the dw bonus. Those two speed modifiers are multiplied for the overall speed.

Example: Hoggar the barbarian wields two 1.3 aps axes with each increased speed by 20% on the weapon. He also has 10% speed on other items and he uses Frenzy (+75%) to attack.

Actual Weapon speed: 1.3*1.2=1.56
Overall Speed: 1.56*(1+0.1+0.15+0.75)=3.12 attacks per second with maximal Frenzy stack.

!There are +0.x aps on items and the math is not yet included!


Besides attacks with cold damage many other skills can inflict a snare effect on your enemy.
Right now we know three snare lvl: light, medium and heavy.

Light snare reduces the movement speed by 30%. This means the enemy needs 1.42 times longer for a given way.

Medium snare reduces the movement speed by 60%. This means the enemy needs 2.5 times longer for a given way.

Heavy snare reduces the movement speed by 80%. This means the enemy needs 5 times longer for a given way.

Different snare effects do not stack only the strongest counts.

Critical Hits

Critical hits are hits with increased damage. The critical hit chance is the percentage chance to score a critical hit with any attack, the base value is 5%. The critical damage is the damage critical his deliver compared to the non critical damage of the attack. The base critical damage is 150%. Both, critical hit chance and critical hit damage can be increased through skills and items. Most classes have several active or passive skills that use critical hits as trigger for additional effects like extra damage or resource generation.

Advanced Game Mechanics

Magic Find:

Magic find is an attribute that can only be found on items. It comes in percentage and does sum up. The number is not your absolute chance to find magic items. It is a factor that does increase your chances to find magic or better items from monster or chests or other container in the gameworld. Every object and monster has a certain base chance to drop better than avarage items, these base numbers are multiplied by your magic find. The chance to find a specific item ( for example one special legendary axe you search for) is also modified by the monster class and if it is elite and of course the monster lvl and the item lvl.

Basic example, numbers are made up for understanding:

Lvl 51 Zombie, Chance to drop:
magic: 3%
rare: 0.1%
legendary: 0.0001%

Your hero has +200% magic find this changes the numbers to:
rare: 0.3%
legendary: 0.0003%

Magic find does not make the items the monster can drop “better” but it increases the chance to find the best items it can drop.

Skill Scaling:

This one is actually not proven yet. But we have several hints that this mechanic is part of the game. Effects/Skills/Runes that are bound to happen on a special trigger like on hit or on critical hit seem to have an build in skill scaling factor. Exceptions are cases where it is stated that it always happens on trigger or on death effects like Rupture.
One example where we were able to confirm this is +health on hit from items. CyberianK made a nice test run for us to confirm the proc on several skills. It did show that the bigger the aoe of an skill was the smaller the actual proc number became. In this case it did proc on every attack but with smaller numbers than you would expect.
Rune effects like Into the Fray do state in their description that they will not always proc but with a certain chance. This chance will be linked to the skill you use to get the proc.
This mechanic is needed to balance the game. If not many aoe abilities or attacks that use high speed animations would otherwise break the game balance.

link to the test numbers from CyberianK:

Stacking of dots:

Damage over time effects do not stack in diablo 3. Everytime you use the same dot on the same target you do only reset the timer to the maximum duration. This does prevent extreme damage numbers from long time dots. The dot effects are balanced to make good damage over a longer time allowing you different actions in the mean time. They have the best damage to cast time ratio.

Dual Wield:

Because many players are badly informed how dual wield works I decided to include a short chapter about it at this point.

If you carry one weapon in each hand you get a 15% speed bonus that does get sumed up with the gear speed bonus (pls look at attack speed calculation for reference). Attacking while dw does alternate the weapon you use to attack.
You do not attack with both weapon at the same time. Many high damage skills use always the damage from the main hand. This was introduced to make dw more reliable.
If one or both weapon carry +0.x attacks per second affix than the bonus speed will be added to both weapons. This is a bonus only dw can get as off hand items can not get this kind of affix. It is a very strong dps increase and should you should always try to get it on your weapons.

Because of the way attack speed is calculated you can get very high aps. With Frenzy full stack and high end equip even 7 or more attacks are possible if not caped somewhere.
When you reach very high attack speed you will run into an loss of efficiency with most builds. If your build does rely on build up and burn phases you will shorten those times to a point that you start to waste time with to much build up or to fast spender spamming while the target mob is already dead. If you run into this problem you should favor damage and defense over more attack speed. Builds without any resource managemant like fury less builds do gain the full benefit of attack speed as they can spam their main attacks without break.

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9 Responses

  1. Filousov says:

    A question – for Demon Hunter:
    Does restraint/focus 2 set bonus add additively or multiplicatively with 6 set unhallowed essence bonus?

  2. Very nice site, i found it on google.

    I like the simplicity of the site, and how good and short you explain stuff, also links are apreciated.

    Bookmarked you and will sure visit again to check new updates.


  3. Anonymous says:

    Thanks a lot, Rhaloz!
    Very helpful information on the damage mitigation in D3.

  4. Anonymous says:

    Nice short and informative. Ty.

    I can finally start a critical hit build now that I have a basic understanding of the mechanic. It makes me wish I hadn't been so quick to throw out some of my critical hit gear that seemed lack luster.

  5. Anonymous says:

    If i DW a main hand with 1 aps and an offhand with a 2aps which of the following scenarios are correct:

    a)1 attack with main hand, wait 0.5 secs and attack with offhand, then wait 0.5 secs and attack with the main hand again.

    b) 1 attack with the main hand, wait 0.5 secs and attack with the offhand, then wait 1sec and attack with the main hand again.

  6. Can you pls explain the difference between 2-handed weapons and 1-handed weapons because when equiping 2-handed weaponds i get like 3k dps

  7. Anonymous says:

    THANK YOU for compiling this info. May I ask what the original source is?

  8. Rustanator says:

    I just wanna let you know I am so happy I found this blog. I hope you keep it up.

  9. Anonymous says:

    What about dmg mechanics? i.e. how much str/int and weapon dps is calculated into equation

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