Chance to Block Mechanics

Chance to Block

Table of Content

  1. Introduction
  2. Mechanics
  3. What can be blocked?
  4. Calculation
  5. Base Chance to Block
  6. Increased Chance of Blocking
  7. Block Rate
  8. Mercenaries and Pets
  9. Monsters with Chance to Block
  10. Summary

Introduction

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

Shield BaseAmazon
Assassin
Barbarian
Druid
Necromancer
Sorceress
Paladin
Buckler25%20%30%
Small Shield30%25%35%
Large Shield37%32%42%
Spiked Shield35%30%40%
Kite Shield33%28%38%
Bone Shield45%40%50%
Tower Shield49%44%54%
Gothic Shield41%36%46%

Exceptional Shields

Shield BaseAmazon
Assassin
Barbarian
Druid
Necromancer
Sorceress
Paladin
Defender35%30%40%
Round Shield37%32%42%
Scutum39%34%44%
Barbed Shield42%37%47%
Dragon Shield43%38%48%
Grim Shield45%40%50%
Pavise49%44%54%
Ancient Shield41%36%46%

Elite Shields

Shield BaseAmazon
Assassin
Barbarian
Druid
Necromancer
Sorceress
Paladin
Heater47%42%52%
Luna45%40%50%
Hyperion49%44%54%
Blade Barrier45%40%50%
Monarch47%42%52%
Troll Nest45%40%50%
Aegis49%44%54%
Ward49%44%54%

Auric Shields (Only Paladin)

Only a Paladin can equip Auric Shields, however, when other Characters look at an Auric Shield, their tooltip shows the % Chance to Block using their Character's bonus.

Normal:

Shield BaseChance to Block
Targe40%
Rondache45%
Heraldic Shield50%
Aerin Shield52%
Crown Shield55%

Exceptional:

Shield BaseChance to Block
Akaran Targe40%
Akaran Rondache45%
Protector Shield50%
Gilded Shield52%
Royal Shield55%

Elite:

Shield BaseChance to Block
Sacred Targe60%
Sacred Rondache58%
Kurast Shield55%
Zakarum Shield52%
Vortex Shield49%

Voodoo Heads (Only Necromancer)

Only a Necromancer can equip Voodoo Shields, however, when other Characters look at a Voodoo Shield, their tooltip shows the % Chance to Block using the Character's bonus.

Normal:

Shield BaseChance to Block
Preserved Head23%
Zombie Head25%
Unravaler Head28%
Gargoyle Head30%
Demon Head32%

Exceptional:

Shield BaseChance to Block
Mummified Trophy23%
Fetish Trophy25%
Sexton Trophy28%
Cantor Trophy30%
Hierophant Trophy32%

Elite:

Shield BaseChance to Block
Minion Skull23%
Hellspawn Skull25%
Overseer Skull28%
Succubus Skull30%
Bloodlord Skull32%

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

1)The tooltip, when hovered over, shows the % Chance to Block, using a Barbarian.

Regular Shields:

ShieldsIncreased
Chance of Blocking
Magic Shield of Blocking1
Rare Shield1
10%
Magic Shield of Deflecting1
Rare Shield1
20%
Caster Crafted Shield5-10%
Hit Power Crafted Shield5-10%
Rhyme20%
Sanctuary20%
Sigon's Guard20%
Civerb's Ward15%
Whitstan's Guard55%
Taebaek's Glory25%
Pelta Lunata20%
Umbral Disk30%
Stormguild30%
Swordback Hold20%
Steelclash25%
Bverrit Keep10%
The Ward10%
Visceratuant30%
Moser's Blessed Circle25%
Stormchaser20%
Gerke's Sanctuary30%
Radament's Sphere20%
Spirit Ward20-30%
Stormshield25%

Auric Shields:

Auric ShieldsIncreased
Chance of Blocking
Herald of Zakarum30%
Griswold's Honor20%
Alma Negra20%

Voodoo Heads:

Voodoo Heads:Increased
Chance of Blocking
Homunculus40%
Trang-Oul's Wing30%

Other Sources

SourceIncreased
Chance of Blocking
Eld Rune socketed in a Shield7%
Safety Crafted Amulets1-10%
Full Isenhart's Armory Set bonus30%
Twitchthroe25%
Guardian Angel20%
Swordguard20%

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 exception to this rule is Guardian Angel.

Calculations

Note for the calculations:

  • ceil = round up the term that follows
  • floor = round down the term that follows

Before we can use the formulas for Block Rate, we need the following values:

  • The total +xx% Faster Block Rate from our gear.
  • The "Block Base" of the Character. Check in the table below.
  • The "Animation Speed" of the Character. Check in the table below.

With these values, we can go through the following formulas.

Effective Faster Block Rate (EFBR):
EFBR = floor(FBR * 120 / (FBR + 120))

With Holy Shield:
EFBR = floor(FBR * 120 / (FBR + 120)) + 50

Block Frames:
Block Frames = ceil(256 * Block Base / floor(Animation Speed * (50 + EFBR) / 100) - 1)

CharacterBlock BaseAnimation Speed
Amazon3256
Amazon (1-handed Weapons) (*)388
Assassin3256
Barbarian4256
Druid6256
Werewolf5256
Werebear5200
Necromancer6256
Paladin3256
Sorceress5256

(*) This only means: 1-handed Axes, Clubs, Maces, Hammers, Scepters, Swords, Throwing Axes.

Practical Example

Practical example with 50 FBR on a Paladin without Holy Shield:

Effective Faster Block Rate (EFBR):
EFBR = floor(50 * 120 / (50 + 120))
EFBR = floor(6,000 / 170)
EFBR = floor(35.294...)
EFBR = 35

Block Frames:
Block Frames = ceil(256 * 3 / floor(256 * (50 + 35) / 100) - 1)
Block Frames = ceil(768 / floor(256 * 85 / 100) -1)
Block Frames = ceil(768 / 217 - 1)
Block Frames = ceil(2.539...)
Block Frames = 3

This means the Paladin with 50 FBR and without Holy Shield uses 3 Frames for the Block animation.

Practical example with 50 FHR on a Paladin with Holy Shield:

Effective Faster Block Rate (EFBR):
EFBR = floor(50 * 120 / (50 + 120)) + 50
EFBR = floor(6,000 / 170) + 50
EFBR = floor(35.294...) + 50
EFBR = 85

Block Frames:
Block Frames = ceil(256 * 3 / floor(256 * (50 + 85) / 100) - 1)
Block Frames = ceil(768 / floor(256 * 135 / 100) -1)
Block Frames = ceil(768 / 345 - 1)
Block Frames = ceil(1.226...)
Block Frames = 2

This means the Paladin with 50 FBR and with Holy Shield uses 2 Frames for the Block animation.

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

1-Handed Swinging Weapons (Axes, Clubs, Maces, Scepters, Swords, Throwing Axes, and Wands):

Faster Block Rate04611152329405680120
Block Frames1716151413121110987

Other Weapons:

Faster Block Rate0133286
Block Frames5432

Assassin

Faster Block Rate0133286
Block Frames5432

Barbarian

Faster Block Rate09204286
Block Frames76543

Druid

Human form:

Faster Block Rate061320325286
Block Frames111098765

Werewolf:

Faster Block Rate0715274886
Block Frames987654

Werebear:

Faster Block Rate051016274065109
Block Frames12111098765

Necromancer

Faster Block Rate061320325286
Block Frames111098765

Paladin

Without Holy Shield:

Faster Block Rate0133286
Block Frames5432

With Holy Shield:

Faster Block Rate086
Block Frames21

Sorceress

Faster Block Rate0715274886
Block Frames987654

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

  • Monsters with no value in the Normal column don't spawn in normal. They are guest monsters throughout Act 5 in Nightmare and Hell difficulty.
  • Monsters with no value in Normal and Nightmare don't spawn in these difficulties. They are guest monsters in the Pandemonium Event (see Ubers article) in Hell.
MonsterNormalNightmareHell
Dark Hunter12%12%12%
Vile Hunter18%18%18%
Dark Stalker25%25%25%
Black Rogue33%33%33%
Flesh Hunter40%40%40%
Flesh Hunter--40%
Fallen9%9%9%
Carver16%16%16%
Devilkin25%25%25%
Dark One36%36%36%
Warped One49%49%49%
Carver-49%49%
Devilkin-49%49%
Dark One-49%49%
Huntress15%15%15%
Sabre Cat20%20%20%
Night Tiger25%25%25%
Hell Cat30%30%30%
Sabre Cat-15%15%
Skeleton10%10%10%
Returned15%15%15%
Bone Warrior20%20%20%
Burning Dead25%25%25%
Horror30%30%30%
Bone Warrior-30%30%
Returned-30%30%
Returned--30%
Slinger15%15%15%
Spear Cat16%16%16%
Hell Slinger19%19%19%
Spear Cat16%16%16%
Night Slinger17%17%17%
Slinger-19%19%
Slinger-19%19%
Slinger-19%19%

Block without Shield

MonsterNormalNightmareHell
Doom Knight124%24%24%
Hollow One20%15%33%
Guardian20%15%33%
Unraveler20%15%33%
Horadrim Ancient20%15%33%
Unraveler20%15%33%
Andariel0%20%40%
Duriel0%25%50%
Mephisto20%40%50%
Diablo25%40%50%
Baal40%45%55%
Baal (clone)40%45%55%
Diablo clone--50%
Lilith--40%
Uber Duriel--50%
Uber Mephisto--50%
Uber Diablo--50%
Uber Baal--55%
  1. Applies to Doom Knights in Act 4 only. Doom Knights in Act 5 cannot block.
  2. Applies to those spawning in Act 2 and Act 3, as well as Achmel the Cursed and his Minions in Act 5. Other monsters of this type spawned in Act 5 cannot block.

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.

Post by Teo1904

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!

Good Luck!