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Damage Calculations
The main goal of the game is to sink Abyssals. Abyssals are sunk by doing Damage to them. This page lists all the applicable formulas and mechanics that affect the calculation of Damage.
Please note that all formulas between [math]\displaystyle{ \lfloor \ \rfloor }[/math] or marked with [math]\displaystyle{ \downarrow }[/math] are rounded down.
 For example, [math]\displaystyle{ \lfloor 4.2 \rfloor = 4 }[/math].
 [math]\displaystyle{ 4.2 \times_\downarrow 1.5 = \lfloor 4.2 \times 1.5 \rfloor = \lfloor 6.3 \rfloor = 6 }[/math], but [math]\displaystyle{ 4.2 \times_\downarrow 1 = 4.2 }[/math] (by definition, [math]\displaystyle{ \times_\downarrow }[/math] is then a noncommutative nonassociative operator, it is assumed to be leftassociative with lower priority than the usual multiplication operator).
 [math]\displaystyle{ \times_\downarrow }[/math] is used when the round down applies only when the modifier is applied.
Damage Formula
The Damage is the reduction of HP caused by an attack hitting a target. The formula is the same for all attacks as well as abyssals. It stems from the difference between the final attack power of the assailant and the defense power of the target.
Damage Formula  

 

Defense Power
Defense power represents the ability of a ship to resist damage. It's calculated from the Armor plus a random element.
Defense Formula  

 

For short, defensive power randomly varies between 1.3 x and 0.7 x.
Attacks Power
Attack power represents the ability of a ship to inflict damage. It's affected by a lot of different elements (stats, mechanics, "battle state", etc.) through 4 steps of calcul:
 Basic
 Generally calculated from the relevant stats of the ship using different formulas according to the type of attack and the phase of battle
 Precap
 The basic attack goes through different modifiers
 Cap
 If the attack is superior to a cap it's reduced
 Postcap
 These modifiers are more potent because they are not limited by the cap
Attack Step Formulas  

Precap

 
Cap

The attack is then capped as follows:
 
Postcap

Capped attack is then modified by postcap modifiers:

Basic Attack Power Formulas
The following section details the different formulas to calculate [math]\displaystyle{ \text{Atk}_\text{base} }[/math]. As the formula depends on the type of attacks and the combat phase.
Below are the common variables used in all accuracy formulas:
 [math]\displaystyle{ \text{FP} }[/math] is the Firepower of the ship including equipment.
 [math]\displaystyle{ \text{TP} }[/math] is the Torpedo of the ship including equipment or the torpedo of a plane.
 [math]\displaystyle{ \text{ASW} }[/math] is the Antisubmarine of the ship or equipment.
 [math]\displaystyle{ \text{DB} }[/math] is the Dive bombing of the plane.
 [math]\displaystyle{ \bigstar }[/math] is the upgrade bonus of the equipment.
 See Improvement or Akashi List for upgrade bonus values.
 [math]\displaystyle{ \text{Count}_\text{Plane} }[/math] is the remaining amount of planes in a slot, performing the attack.
 [math]\displaystyle{ \text{Mod}_\text{CF} }[/math] is the combined fleet modifier based on the tables below:
Combat Phase  Forces  Carrier Task Force  Surface Task Force  Transport Escort Force 

Main Fleet Shelling  Allies  +2  +10  5 
Enemy  +10  +5  +10  
Escort Fleet Shelling  Allies  +10  5  +10 
Enemy  +5  5  +5  
Torpedo  Allies  5  5  5 
Enemy  5  5  5 
Combat Phase  Forces  Carrier Task Force  Surface Task Force  Transport Escort Force 

Main Fleet Shelling  Allies  +2  +2  5 
Enemy  +10  +10  +10  
Escort Fleet Shelling  Allies  5  5  5 
Enemy  5  5  5  
Torpedo  Allies  +10  +10  +10 
Enemy  +10  +10  +10 
Combat Phase  Forces  Bonus 

Vs Main Fleet  Allies  +5 
Enemy  +10  
Vs Escort  Allies  +5 
Enemy  5  
Torpedo  Allies  +10 
Enemy  +10 
Airstrike
The damage from airstrikes is calculated independently for each plane slot and mainly depends on the stats of the plane and the current plane count of the slot.
Airstrike Attack Formula  

 
This applies to Jet Assaults and Airstrikes. 
Surface Shelling
The surface shelling damage stems directly from the Firepower of the ship.
Surface Attack Formula  

 
This applies to most ships during the Shelling phase (unless it is an ASW attack). 
Carrier Shelling Attacks
Unlike during airstrikes, carrier shelling does not depend on the plane slot and instead combines the stat of the carrier and all planes equipped to one attack.
Carrier Shelling Attack Formula  

 
This applies to carriers during the Shelling phase (unless it is an ASW attack).

Torpedo Attacks
Torpedo damage stems directly from the Torpedo of the ship.
Torpedo Attack Formula  

 
Torpedo Attacks only include the Opening Torpedo Salvo and Closing Torpedo Salvo. 
AntiSubmarine Warfare
 For more information on this topic, see AntiSubmarine Warfare.
The stats used to calculate damage against submarines is the ASW.
 When contributing to ASW power, Base ASW is square rooted, while equipment ASW is multiplied by 1.5.
 Antisubmarine weaponry is therefore the primary source of ASW damage, with the base ship ASW playing a very minor role damagewise.
 However, base ship ASW is the primary determinant of whether a ship can reach 100 total ASW to perform "Opening ASW" (OASW) attacks.
 Unlike shelling, ASW damage is capped at 170.
ASW attacks have different modifiers gained from Formations,
 Line Abreast is the main ASW formation, with a 1.3x damage modifier,
 Cruising Formation 1 is the main ASW formation for Combined Fleets, with a 1.3x damage modifier.
AntiSubmarine Formula  

 

Surface Night Battle
Night battle damage stems directly from the sum of Firepower and Torpedo of the ship.
Night Attack Formula  

 
This applies to most ships during Night Battle. 
Carrier Night Air Attacks
The carrier night air attack damage calculation is complex but for short only take the stat of the night plane.
Carrier Night Air Attack Formula  

 
This applies to carrier night air attack 
AntiInstallation Attacks
 For more information on this topic, see AntiInstallation.
Installations differ from regular enemy warships, as they are immune to certain attack elements like the torpedo stat, but are extremely weak against specialized gears.
Support Expedition Attack Power Formula
Support Expedition attack formulas are close but not the same as combat formulas. They also are only affected by the following modifiers:
Shelling Support
Basic attack power is calculated in a similar way as normal for surface ships and carriers except that firepower is reduced by 1.
Surface Attack Formula  

 

Carrier Shelling Attack Formula  

 

Airstrike Support
Airstrike Support Attack Formula  

 

AntiSubmarine Support
AntiSubmarine Support Attack Formula  

 

Long Range Torpedo Support
LongRange Torpedo Attack Formula  

 

LBAS Attack Power Formulas
 For more information on this topic, see LBAS.
AntiShip  

Precap

 
Postcap


AntiInstallation  

Precap

 
Postcap


ASW  

Precap

 
Postcap

 

 Notes
 Unlike carrier airstrikes, the 1.2x critical proficiency bonus applies to each slot independently.
 Jet Assault use the airstrike formula even on land base.
Attack Power Corrections
After calculating the basic attack power of the attack being made, it is then adjusted based on various factors. Attack power modifiers can be split into pre and postcap modifiers. Postcap modifiers are more powerful to have because they aren't reduced by the cap.
Precap Modifiers
Engagement
 For more information on this topic, see Engagement.
Form  Common name  Damage Modifier  Chance  Chance with Saiun 

Crossing the T (Advantage)  Green T  1.2  15%  15% 
Parallel Engagement  Parallel  1.0  45%  45% 
Headon Engagement  Headon  0.8  30%  40% 
Crossing the T (Disadvantage)  Red T  0.6  10%  0% 
 Engagement modifier affects the Shelling Phase, as well as the Battle Openings, the Closing Torpedo Salvo, and Support Expeditions.
 All engagement forms affect both sides equally, including Green T and Red T.
 The exception are ASW and some Special Attacks.
 Night Battle and Aerial Combat are not affected by engagement.
Formation
 For more information on this topic, see Formation.
Formation Attack Power Modifiers  

Formation  Shelling  Torpedo  ASW  Night Battle 
Line Ahead  1.0  1.0  0.6  1.0 
Double Line  0.8  0.8  0.8  1.0 
Diamond  0.7  0.7  1.2  1.0 
Echelon  0.75  0.6  1.1  1.0 
Line Abreast  0.6  0.6  1.3  1.0 
Vanguard  0.5  1.0  1.0  0.5 
1.0  1.0  0.6  1.0 
Combined Fleets have special formations that differ from the standard single fleet formations. The following formations can be selected.
The following tab resume when engagement and formation are effective:
Modifier  LBAS  Airstrike  Support  Shelling  Torpedo  ASW  Night Battle  

Shelling  Aerial  Torpedo  Surface  Carrier  
Engagement  ❌  ✔️  ✔️  ❌  ✔️  ✔️  ✔️  ✔️  ❌  ❌* 
Formation  ❌  ❌  ✔️  ❌  ✔️  ✔️  ✔️  ✔️  ✔️  ✔️ 
 Note
 If one of the fleet si a combined one then the formation modifier become 1 for the support.
Damage State
Damage State  Shelling  Torpedo  ASW 

Not Damaged  1.0  1.0  1.0 
Lightly Damaged (小破)  
Moderately Damaged (中破)  0.7  0.8  0.7 
Heavily Damaged (大破)  0.4  0  0.4 
 Notes
 Damage state does not affect aerial combat.
 It will affect carrier attacks in the shelling phase.
Night Battle CutIn
 For more information on this topic, see Night CutIn.
Night CutIns will apply extra modifiers if triggered.

ASW Synergy
ASW Damage Synergy  

Small Small Sonars  
Large Large Sonars  
DCP Depth Charge Projectors (DCP)  AP AP  
DCR Depth Charge (Racks) (DCR)  AP AP AP AP AP  
Other ASW Mortars  
ASW Damage Modifiers: [math]\displaystyle{ \text{Mod}_\text{synergy} = {Mod}_\text{1} \times {Mod}_\text{2} }[/math]  
[math]\displaystyle{ {Mod}_\text{1} }[/math]  + (Any Sonar + Any Depth Charge) 
1.15  
[math]\displaystyle{ {Mod}_\text{2} }[/math]  DCP + DCR and NO Small  1.1  
Small + DCP + DCR  1.25  
Examples  
[math]\displaystyle{ \text{Mod}_\text{synergy} }[/math]  Small + DCP + DCR  1.4375[math]\displaystyle{ 1.15 \times 1.25 }[/math]  
Large + DCP + DCR  1.265[math]\displaystyle{ 1.15 \times 1.1 }[/math]  
Armor Penetration  
Indepentant of synergies, some equipment provides additional armor penetration to ASW attacks.
The flat armor penetration value is calculated as follows:

Special Attack Bonus
 For more information on this topic, see Special Attacks.
The Special attacks modifier are postcap for day battle. But are precap for night battle.
Hidden Fit Bonuses
 For more information on this topic, see Hidden Fit Bonuses.
Unlike the other precap bonuses, this is just a minor additive firepower bonus added for some ships (mostly cruisers) when equipped with certain guns.
Postcap Modifiers
Aerial Contact
 For more information on this topic, see Aerial Combat#Contact.
During aerial combat, there is a chance for the ships to trigger Contact. When it is triggered, the is a bonus multiplier applied to airstrike damage depending on the Accuracy of the plane that triggered contact.
Accuracy  Damage Modifier 

0  1.12 
1  1.12 
2  1.17 
3+  1.2 
Airstrike Special Bonus
There's a bonus when attacking certain Princess and Demontype enemies during airstrike. The multiplier is chosen randomly between two values. The chance is roughly 50%.
[math]\displaystyle{ \text{Mod}_\text{boss} }[/math]^{[3]}  

Boss (ID)  Low mod  High mod 
PT Imp (16371640)  0.5  0.8 
BB Hime (1557)  1.4?  2.2? 
Summer BB Hime (16961698)^{[4]}  1.3?  1.8? 
CV Hime (1586)  1.7?  2.2? 
CV Hime B (21052108)  1.7?  2.2? 
 ↑ ^{1.0} ^{1.1} ^{1.2} Tashkent Kai only.
 ↑ NB CVCI [1]
 ↑ https://twitter.com/Divinity_123/status/1659942254671216642
 ↑ https://x.com/yukicacoon/status/1820489203710611821
Artillery Spotting
 For more information on this topic, see Combat/Artillery Spotting.
Attack Type  Prerequisites  Postcap Damage Modifier 
Notes 

Main Zuiun Cutin (Zuiun CI) 
1.35  Iseclass Kai Ni only  
Main Suisei Cutin (Suisei CI) 
1.3  
Main AP Shell Cutin (APCI) 
1.5  
Secondary AP Shell Cutin (Sec APCI) 
1.3  
Secondary Radar Cutin (Radar CI) 
1.2  
Secondary Cutin (Sec CI) 
1.1  
Double Attack (DA) 
1.2 
Carrier CutIn Attacks
 For more information on this topic, see CVCI.
Attack Type  Prerequisites  Postcap Damage Modifier 

FighterBomberAttacker (FBA) 
1.25  
BomberBomberAttacker (BBA) 
1.2  
BomberAttacker (BA) 
1.15 
If a CVCI attack is evaded, it will deal Scratch Damage instead.
ArmorPiercing Modifier
During day combat, certain enemy ships take extra damage from AP Shells
.
 The bonus only applies against FBB, BB, BBV, CV, CVB, CA, and CAV.
 This includes Installations.
 This means that this bonus does not apply against all other types, namely CVL, CL(T), CT, DD, DE, SS(V), AV, AS, AR, LHA, or AP.
For clarity purposes:
 is used to indicate a Main Gun of any size,
 is used to indicate a Secondary Gun of any size,
 is used to indicate an AP Shell,
 is used to indicate a Radar of any type,
Type  Modifier 

1.08  
1.10  
1.15 
 Note
 It is unadvisable to run any of the other setups beyond the most basic Gun+AP, as the other setups will interfere with artillery spotting and give worse bonuses.
 This modifier doesn't affect support shelling.
Barrage Balloon Modifier
Barrage Balloons can be deployed in certain situations during day battles.
 Barrage Balloons can only be deployed on certain combat nodes with Installations
Compatible Nodes  

Map  Node  Notes  
35  H  
43  N  Boss  
45  T  Boss  
64  N  Boss  
Events  Refers to the current event page  
references  [6][7][8][9] 
 Once deployed
 For every ship with a balloon equipped will boost the damage of the fleet and the LBAS (postcap):
Balloon Effects  

1  2  3  
Allied Day Shelling Damage  
Allied balloons [10]  1.02  1.04  1.06 
Allied LBAS Damage  
Allied balloons [11]  1.02  1.04  1.06 
Enemy balloons [12]  0.95  0.90  0.85 
 The effect stacks up to 3 balloons, and up to 1 balloon per ship,
 The effect applies to LBAS and day shelling, with the enemy balloons also negatively affecting allied LBAS,
 The effect does not apply to torpedo phases or night battles,
 If the ship deploying it is sunk, the balloon is then removed, as well as its effects.
AntiInstallation Equipment Modifiers
 For more information on this topic, see AntiInstallation.
Special Attack Bonus
 For more information on this topic, see Special Attacks.
The Special attacks modifier are postcap for day battle. But are precap for night battle.
Criticals
For more details on how critical chance is calculated, please see Critical.
 Normal Criticals
Attack Type  Modifier 

Normal  1.0 
Critical  [math]\displaystyle{ 1.5 \times \text{Mod}_\text{proficiency} }[/math] 
 Plane Proficiency Critical Modifier
 For more information on this topic, see Plane Proficiency.
Ammunition Modifier
The damage of the fleet is reduced once their ammunition falls below 50%. This modifier cannot go above 1. The formula used to determine this is:
[math]\displaystyle{ \text{Ammo} }[/math] formula  


Remaining Ammo  Ammo Modifier  Notes 

>50%  1.0  
40%  0.8  4th Battle 
30%  0.6  
20%  0.4  5th Battle 
10%  0.2  
0%  0  6th Battle 
 The battle number indicated in the notes assumes only normal surface engagements. Engaging in night battles and other special engagements can change that number.
 Whatever ammunition modifier applies in day battle carries over to night battle.
 Maelstroms that reduce ammunition also count towards this modifier.
 Using Underway Replenishment is a way to medigate ammo penalties.
 The ammunition modifier affects aerial battle.
 Once a ship hits 0% ammo, all attacks become scratch damage.
 Debuffs are affected by the ammunition modifier.
Miscellaneous Damage Modifiers
Scratch Damage
In the following cases, attacks will deal "scratch damage" instead of normal ones:
 If a Cutin or a special attack is evaded;
 The target's armor cannot be penetrated (attack inferior to eh enemy defense);
 The ammo count hits 0;
 When a single fleet attack submarine at night;
 When a Friendly Fleet attacks the last remaining ship of an enemy fleet.
Scratch damage is dealt as a percentage of remaining HP calculated using the following formula:
Scratch Damage formula  

Therefore the maximum possible scratch damage [math]\displaystyle{ \text{HP}_\text{current} \times 0.14  0.08 }[/math] and the minimum damage is [math]\displaystyle{ \text{HP}_\text{current} \times 0.06 }[/math].
 
A Friendly Fleet cannot kill the last ship of the opposing fleet, dealing special scratch damage instead.

 Scratch damage is generally between 614% of current HP.
The target's HP cannot be reduced to 0 (and therefore sunk) by scratch damage.
PT Imps
AntiPT boat  

Unlike most standard Abyssals, "PT boats" (PT Imp Pack & Schnellboot Imp Pack) are "very small and fast".
During Events, some special bonuses may be added, with "historical" ships and equipment gaining some accuracy bonuses^{[10]}.
 
[edit] 
Historical Bonus
On almost every Event map, as well as some regular maps (74 & 75 so far), certain ships, types of ships, equipment, or types of equipment will bring bonuses.
 Those bonuses are most of the time raw damage multipliers, and sometimes, accuracy bonuses.
 Bonuses are independent to each ship, so only the ships with any historical bonus or ships equipped with historical equipment will be affected.
 Bonuses may be applicable to some parts of a map only, such as specific phases of nodes.
This mechanic is here to encourage the use of "historically significant fleets and setups".
 By nature, historical bonuses are arbitrary, so refer to each individual map to see what bonuses are applicable.
Summer Mode Bonuses
There are consistent bonuses against the following abyssal bosses' summer forms. These bonuses may differ on some event's maps.
Damage Bonuses  

Ships [Toggle Names] 
1.1x    
  1.15x  
Equipment  AP Shells 
1.2x  1.1x  1.1x  1.2x 
Bomber SPB SPF 
1.1x  1.15x  1.1x  1.1x  
Bomber Laté 298B    1.32x1.1 x 1.2  
Swordfish 
1 = 1.15x 2 = 1.32x 
1 = 1.15x 2 = 1.21x 
1 = 1.1x 2 = 1.21x 
  
Dive Bombers    1 = 1.1x 2 = 1.32x 
1 = 1.1x 2 = 1.265x 
The Laté 298B bonus includes the SPB bonus.
Debuffs
Debuffs are a special case that only applies during events.
Certain event maps have debuff mechanics that require completing certain gimmicks once Last Dance is reached, in order to trigger the boss or boss' fleet debuff.
 See here for more details on past event debuffs.
Debuffs can be either:
 A reduction to the enemy's armor ,
 A postcap damage modifier for the attacking fleet (probably cases of miss interpretation of armor reductions).
Overkill Protection
When a ship in the fleet takes more damage than her current HP, she will take a percentage of her current HP in damage instead.
 The ship must be the flagship OR
 The ship must not be heavily damaged (大破) nor red morale at the start of the battle.
 If the ship has red morale, she will just have her HP reduced to 1.
Overkill formula  

 

Overkill protection will take off between 5080% of the ship's current HP .
 Important Information
 In general:
 Overkill protection is most applicable to DDs.
 The most pronounced effects of overkill protection occur at low HP
 It is also the primary means of surviving a hit they fail to evade
 For example, a 32HP DD has a 15.5% chance of being heavily damaged (大破) by a BB Hime, while a 31 HP DD has just a 6.5% chance
 This has great implications when marrying ships, 36 HP has one of the highest chances of a taiha
 Oddnumbered HP is better when overkill protection is triggered. This is because the damage calculations round down, reducing the likelihood of being knocked down to heavy damage.
 This mechanism is most applicable to ships at full HP. Once a ship starts taking damage, the utility of overkill protection diminishes
 Overkill protection is most applicable to DDs.
 Generally ships with HP that are divisible by 4 have worse survivability.
See Also
