Combat/Damage Calculation

Main Formula

Basic Attack Power

 * Multiple SONAR/Depth charges do not boost the ASW Bonus (i.e. 2 of each still makes the bonus 1.15)
 * Please read Akashi's Improvement Arsenal page for effects given by upgraded equipment.
 * Please read Combined Fleet page for combined fleet factor in combined fleets.
 * All carriers that participate in night battle, including friendly side and abyssal's, use the standard night battle formula.
 * During Night Battle, the basic attack power of anti-submarine warfare can be treat as zero, with the exception of in Combined Fleet maps and Night Battle nodes.

Pre-Cap Modifiers
These are the factors directly applied to your ship's attack power. Effects from the modifiers are multiplied/added cumulatively.
 * Anti-Installation Attack Modifier
 * Formation Modifier (see "Damage modifier")
 * Engagement Modifier
 * Health Modifier
 * Plane Scaling (Opening air strike only)
 * Night Special Attack Modifier
 * Light Cruiser Fit Bonus

Anti-Installation Attack Modifier
Note also that against installations, only Firepower is taken into account; in night battle, even though attack power is normally the sum of Firepower and Torpedo, for installations specifically the Torpedo stat is disregarded.
 * The Type 3 Shell multiplies Firepower by 2.5.
 * The WG42 (Wurfgerät 42) adds at least 75 Firepower, exact number depend on amount of WG42 equipped, see WG42's page. In the event both are present, this is added after the Type 3 Shell's effects, but before the sum is multiplied by the other modifiers.
 * Landing Crafts give varying bonuses against installations.

Ship's Health Modifier
These modifiers do not affect Aerial Combat.

Plane Scaling
Applied on bombers during the opening air strike. These are the random numbers multiplied to the plane's bombing attack power.

Night Special Attack Modifier
Certain Equipment setups have a chance to trigger special attacks at night, giving boost to both attack power and accuracy. This stage is usually the most rewarding / dangerous because both sides have drastically increased attack power.

The ship must be able to participate in the night battle in order to trigger the special attacks.

Light Cruiser Fit Bonus


a few points would be added for CL's attack power after all pre-cap firepower but before the cap if they used fit guns.
 * Applicable Twin Gun Mounts: 15.2cm Twin Gun Mount, 15.2cm Twin Gun Mount Kai, 14cm Twin Gun Mount
 * Applicable Single Gun Mounts: 15.2cm Single Gun Mount, 14cm Single Gun Mount
 * Not Applicable Guns: All the 15.5cm and 20.3cm guns, OTO 152mm Triple Rapid Fire Gun Mount, 15cm Twin Secondary Gun Mount, etc.

Attack Power Cap
Applies after the pre-cap modifiers. This is a soft limit on your effective attack power.

Condition : If your pre-cap attack power exceeds: The Attack Power Cap will be activated, nerfing the effectiveness of your pre-cap attack power. The calculation is:
 * 150 for Day Battle
 * 300 for Night Battle
 * 100 for Anti-sub attacks

$$\text {Attack Power After Caps} = x + \sqrt {\text {Pre Caps Attack Power} - x}$$, Where x represents the attack power cap.

Daytime Attack Cap (150) often makes it important to utilize Artillery Spotting since they boost your attack power after the cap, Night Combat can be very dangerous and/or rewarding due to having a very high cap (300) and the inclusion of torpedo to firepower for the basic attack power calculation.

Post-Cap Modifiers
In damage calculation, Post-cap modifiers apply after the cap, but before enemy armor reduction. Thus they are very effective approach to boost your damage output (esp. against heavy armor enemies).

Currently, the post-cap modifiers are from:
 * Artillery Spotting (aka. Day time special attacks)
 * Critical Damage and Aircraft Proficiency
 * Contact (Opening air strike)
 * AP Shell (against certain targets)
 * PT Imp Pack (unconfirmed)

Artillery Spotting
Certain equipment setups provide a chance to trigger special attacks during day battle, giving boost to both attack power and accuracy. The damage modifiers are applied after the cap (150), thus very effective against heavy armor targets. Note that the ship requires at least 1 seaplane on board to perform Artillery Spotting.

Critical Modifier
Most forms of attack (Torpedo, Shelling, Anti-Submarine, Preemptive Bombing) have a chance to crit the target. The damage modifier applies after the cap. It should be noted that the critical message always appears when damage dealt is greater than or equal to 40, regardless of whether the 150% modifier was applied or not. On the other hand, the critical message will never appear when damage dealt is less than or equal to 14, even if the 150% modifier was applied.

Critical damage rate seems to depend on accuracy.

Aircraft Proficiency boost Critical Hit Modifier.

Contact
Contact takes place during the Aerial Combat phase. It increases bombing damage for all allied bombers. When successful, an image of the squadron performing contact is shown in the opposing fleet's formation indicator, with the text "触接中". Different types of planes have different trigger rates. They are roughly estimated as (if only one is equipped):
 * Trigger conditions:
 * More air control than Air Denial
 * At least one carrier scout plane, seaplane scout, or torpedo bomber equipped.
 * Seaplane bombers, Type 3 Spotter, and Ka-type Autogyros cannot perform contact.
 * It's thought that each carrier scout plane, seaplane scout, and/or torpedo bomber slot equipped is given a chance to trigger contact. Once successful, the bonus applied is chosen at random with weighting preferential towards higher modifiers from all eligible equipped planes.

Contact Damage Modifier

 * The damage increase depends on the +accuracy bonus of the squadron performing contact.

AP Shell
Damage against certain targets increases when both large-caliber main guns and AP shells are equipped.

This modifier works against the following enemy classes: Notes
 * Battleships (including Fast Battleships and Aviation Battleships)
 * Heavy Cruisers
 * Standard Carriers
 * Demons and Princesses (including land installations)
 * Floating Fortresses (Escort Fortress and Floating Fortress)
 * The AP shell and seaplane used in the tests were Type 91 AP Shell and Type 0 Observation Seaplane.
 * Numbers for the setups involving secondary guns are not confirmed yet, but believed to be near.
 * Has not been tested against Light Cruiser Demon and Destroyer Princess at the moment.
 * Has not been tested against Armored Carriers and Aviation Cruisers as of 02/06/2015.
 * Detailed tests are still ongoing. Values differ slightly from test to test (source). Current values are taken off wikiwiki.
 * Exercise caution as this modifier works for enemy ships as well (practice matches and special enemies with Deteriorate AP Shell equipped).

Remaining Ammo Modifier

 * In general, two bars of will be used in Day Battle for all ships, regardless of whether they attack or not.
 * The Remaining Ammo Modifier affects all phases, including the opening Aerial Combat Phase.
 * When entering night battle, the Remaining Ammo Modifier on a vessel remains same as the previous day battle. One bar of is used for all ships in Night Battle, regardless of whether they attack or not.
 * Because most battles will consume 2 bars of ammunition each, try to engage the boss before the 5th battle, or else achieving victory becomes unlikely (but not impossible).
 * When attempting to defeat boss nodes, avoid night battles and whirlpools on the way.
 * Whirlpools will decrease either or  bars of your sorted fleet, which can be disadvantageous in long sorties.  Equipping one or more ships with RADAR can help reduce losses taken from these.
 * Only one RADAR is required per ship.  Equipping multiple RADAR to the same ship will not reduce the penalty further.
 * The max reduction typically occurs at 3 ships with RADAR.  In events special caveats such as only RADAR in the main fleet of a Combined Fleet being considered can exist.
 * Submarine-only nodes on limited-time event maps do not consume ammo in Day or Night Battle.
 * Hayasui with Underway Replenishment can temporarily resupply ammo/fuel under certain condition.
 * Ammo/Fuel reduced in Air Raid nodes are reduced. Read Events/Mechanics for details.

Player Ship Protection Mechanisms
While the above formulas and statements are generally true for damage taken by a player's ships, there are additional limits that apply to friendly units only. These protection mechanisms are important for game balance and to protect your fleet from sinking.
 * For ships entering battle at chuuha (orange) or higher HP:
 * Damage taken cannot reduce HP below 1.
 * Any further hits will become misses.
 * For flagships, as well as ships with 20 morale or more (i.e. not red face):
 * If damage taken exceeds a ship's current HP, then instead of taking full damage, the damage of the current attack is limited to 50%-79% (rounded down) of current HP.
 * For multi-hit attacks, such as night battle torpedo cut-in attacks, each hit is calculated separately.
 * This can occasionally help ships avoid taiha (red HP), because it narrows the range of damage where it is possible to be hit into taiha.
 * For ships with at full HP and an odd HP total, it is occasionally possible to stop damage at lightly damaged.