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Chance to Block Mechanics

Last Updated: March 6th 2024

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Chance to Block is a mechanic that has defensive and offensive implications. Negating all damage of an attack that has been blocked, it is a significant boost for your survivability when used as an additional layer of defense. To use it as such, you have to sacrifice maximum Life. However, it becomes incredibly important for Characters engaged in front line fights, and for Hardcore in general.

Monsters also benefit from Chance to Block.

Mechanics

  • While wearing a Shield, a Character has a % Chance to Block. This can be seen by hovering over the Defense value on your Character Screen. Chance to Block is capped at 75% while using Skills without movement, standing, walking or using Whirlwind.
  • When running, the % Chance to Block is reduced to 1/3, reducing the cap to 25%.
  • A successful block negates the damage from the incoming attack.
  • The total % Chance to Block is determined using the Character Level (clvl), a Character specific bonus, the base % Chance to Block on the Shield, sources of "x% Increased Chance of Blocking", and the total Dexterity value.
  • The % Chance to Block is applied after an attack successfully passes the hit check but before the Amazon's Dodge, Avoid, and Evade.
  • Successful blocks trigger an animation. The duration of this animation is determined by the Block Rate Breakpoint, which is influenced by the Affix "+x% Faster Block Rate".
  • You can block immediately after the animation of a previous block is over. This can cause you to get into a "Block-Lock".

What can be blocked?

While most attacks can be blocked, there are a number of exceptions. There are also some unintuitive sources of incoming damage that can be blocked. Check out the following table:

Can be blockedCan't be blocked
Melee AttacksLevel 49+ Fire Arrow and Cold Arrow
Fired Arrows and BoltsLightning Bolt
Javelins, Throwing Axes, and Throwing KnivesExplosion of Molten Boulder
Check out the Skill mechanics here.
Missiles with Physical Damage componentThe radial damage of Tornado
Check out the Skill mechanics here.
Death explosions from Bone Fetishes and Suicide MinionsRadial impact damage of Armageddon
Check out the Skill mechanics here.
Explosions from Fire Enchanted ElitesCorpse Explosion
Smite
Charge from Claw Vipers and Reanimated Hordes

Calculations

Dexterity required for 75% Chance to Block

The most frequent question in regard to Chance to Block is: "How much Dexterity do I need to reach 75%"? To calculate this, we need the following 3 variables:

  • Shield = Base Chance to Block of the used Shield, including the Character's bonus
  • Bonus = Sum of all "x% Increased Chance of Blocking" values and Holy Shield when active
  • clvl = Character Level

Formula

Dexterity = 15 + ceil(150 * clvl / (Shield + Bonus))

Example:

Let's put this formula to practice using the Character shown on the right. Our Paladin has 50 Dexterity at Level 73 and has a Skill Level 10 Holy Shield active.

Shield = 52% (see table below!)
Bonus = 37% + 10% + 25% + 30% = 102%
clvl = 73

Dexterity = 15 + ceil(150 * 73 / (52 + 102))
Dexterity = 15 + ceil(150 * 73 / 154)
Dexterity = 15 + ceil(71.1...)
Dexterity = 15 + 72 = 87

Current % Chance to Block

To calculate the current % Chance to Block, we need the following 4 variables:

  • Shield = Base Chance to Block of the used Shield, including the Character bonus
  • Bonus = Sum of all "x% Increased Chance of Blocking" values and Holy Shield when active
  • Dexterity = Total value of Dexterity (Character Screen)
  • clvl = Character Level

Formula

CTB = min(floor((Shield + Bonus) * (Dexterity - 15) / (clvl * 2)), 75) %

Example

Let's put this formula to practice using the Character shown on the right. Our Paladin has 50 Dexterity at Level 73 and has a Skill Level 10 Holy Shield active.

Shield = 52% (see table below!)
Bonus = 37% + 10% + 25% + 30% = 102%
Dexterity = 50
clvl = 73

CTB = min(floor((52 + 102) * (50 - 15) / (73 * 2)), 75) %
CTB = min((floor(154 * 35 / 146)), 75) %
CTB = min(floor(36.9..),75) %
CTB = 36 %

Base Chance to Block

Every Shield in Diablo 2 has a base % Chance to Block, shown in the tooltip. This % is the sum of the Shield's base value and a bonus value, which depends on the Character that looks at the Shield.

Character Bonuses

CharacterBonus Chance to Block
Amazon, Assassin, Barbarian+25%
Druid, Necromancer, Sorceress+20%
Paladin+30%

Shield Values

Adding these values to the Shield bases lead to the following % Chance to Block values displayed in the game, including the Character bonus. If you hover over the Shield name on the left, you can see the base value without the Character bonus, in the following accordions:

Normal Shields

Exceptional Shields

Elite Shields

Auric Shields (Only Paladin)

Voodoo Heads (Only Necromancer)

Increased Chance of Blocking

In the calculation for the total % Chance to Block, the summed up % value of this Affix, across all item slots, is added to the base % Chance to Block of the Shield. If this Affix is on the Shield, it shows in the tooltip of the Shield. It doesn't add to the tooltip, if it comes from other item slots.

Sources

Shields

Other Sources

Block Rate

Blocking is an animation that is performed when you successfully block a physical attack. This includes the Assassins' Weapon Block. Your Block Rate determines how fast this animation is performed.

Mechanics

  • While blocking, you are unable to perform any actions.
  • You can block consecutive attacks, as soon as your animation finishes, potentially leading to a full "block lock".
  • You can speed up the animation by using gear with +xx% Faster Block Rate (FBR).
    • This Affix is exclusive to Shields, making it very hard to come by. The only exceptions to this rule are Guardian Angel and Pattern.

Calculations

Practical Example

Breakpoints

+140% Faster Block Rate (155% on Paladin) is the maximum you can achieve. The tables below show the Breakpoints with achievable Faster Block Rate values.

Amazon

Assassin

Barbarian

Druid

Necromancer

Paladin

Sorceress

Mercenaries and Pets

  • No Mercenary can block attacks. The % Chance to Block from a Shield equipped on the Iron Wolf (Act 3 Mercenary) does not apply.
  • Among all the Pet type minions, only the Necroskeleton (Raise Skeleton) has a 3% Chance to Block when using a Shield.
    Note: The visual model wearing a Shield is actually not an indicator whether it has a Chance to Block.
  • The % Chance to Block from a Shield used to summon an Iron Golem is not applied to the Golem.

Monsters with Chance to Block

Hidden in the game files, monsters receive a % Chance to Block for each difficulty. They only execute that Chance to Block if they either spawn with a Shield and have a blocking animation enabled, or if they are tagged with "NoShldBlock" in the monstats.txt. Check out the tables below, showing what monsters have a Chance to Block with or without Shields.

Spawned WITH a Shield

Block without Shield

Summary

  • Chance to Block is a very good way to mitigate damage taken from attacks.
  • Chance to Block is more dangerous in the early game, than the benefits of Blocking because you have to sacrifice Vitality. Once you have a good Shield, consider speccing into Chance to Block.
  • Hardcore players should consider going for 75% (max) Chance to Block with almost every build.
  • The Block Animation speed is improved by +x% Faster Block Rate.
  • You can get "Block-Locked", meaning you block multiple times in a row and you are not able to take any other actions.
  • Some monsters have a Chance to Block, even if they don’t show the animation.

Phew... This post was longer than expected. As this is a very important mechanic, it is well worth the read. Make yourself familiar with all Chance to Block nuances!

Credits

Written by Teo1904
Reviewed by MacroBioBoi

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