The "hidden fit bonus" mechanic refers to some ships receiving bonuses or penalties when equipping certain equipment, depending on if the equipment "fits" the class or not.

  • This almost exclusively refers to main guns, where each class of ship is engineered to carry up to certain gun calibers, and so, equipping gun turrets of the right caliber or lower will imply an accuracy bonus, whereas using larger calibers will result in some overweight penalties.
  • So far, all fits involve Accuracy Accuracy, and some also affect Firepower Firepower.
  • Not to be confused with visible Equipment Bonuses.

As hidden bonuses are unaffected by morale or fleet types (e.g. combined fleets), it can be interesting to utilize those fit bonuses as much as possible.

How much bonus/penalty a ship receives, depends on:

  • The ship class, larger classes being able to carry larger equipment,
  • If the ship is married or not, married girls having better fits,
  • The size of the gun (caliber and quantity per turret), the larger ones being the most constraining.
  • Some other less frequent factors:
    • The ship's remodel,
    • The ship's speed,
    • Whether it is a day or night battle.

Battleships (F)BB(V) Bonuses

Battleships receive accuracy   bonuses if the guns are fit and penalties if it is overweight[1].

Ship Class IJN 35.6 cm 
 
 

KMS 38 cm 
 

Sov 30.5 cm 
 

RN 38.1 cm 
 

Fr 38 cm 
 
RM 381 mm 
 
IJN 41 cm USN 16 in Twin USN 16 in Triple RN 16 in IJN 46 cm 51 cm Twin 
 
51 cm Triple 
basic 
 
 
Triple K2  Twin K2  Mk.I  Mk.V  Mk.VIII  Mk.7  Mk.7
+GFCS
 
Mk.6
mod.2
 
Mk.I  +AFCT  Kai
+FCR
 
Proto  46cm  Kai 
Gangut-class +7
Sov 30.5 cm: +10
0 +1 -7 ?? -5 ?? -3 -9~10? ?? ?? -7 -18 ?? N/A
Kongou-class +7 0 -2 -5 -5? -5 -6~7? -5 -6 -3 -7 -10 -10?
Bismarck-class
Vittorio Veneto-class
+4 0? +1 -5 -5 -4? -5 ?? ?? -7 -10 ??
Iowa-class +4? 0? -2? -5 0 +2 -7 -10 ??
Colorado-class +1 +2 -2 ?? ?? -7
South Dakota-class -5
M: +4.6
?? ?? ??
Richelieu-class +4 +4~5 -2 -2 -5 -7 -14? -8 -7 -10 ??
Queen Elizabeth-class +6
RN 38.1 cm: +8
+1~2 +2 -2? +5 ?? +3~4 -8 -11 ??
Nelson-class 0 0 +3? 0 0 ?? ?? ??
Fusou-class Kai/Ni
Ise-class Kai
+4 0 +2 +2 0 0? -3 -7
F+: -11?
-4?
Ise-class Kai Ni +4? 0 +1? +4? +4? +6 +2 ?? -7
F+: -11?
??
Fusou-class base
Ise-class base
+2 0 +2 +2 +2 +2? +3 -3 -7 ??
Nagato-class base/Kai 0 ??
Nagato-class Kai Ni +2? 0 +1? +5 +5 +5~6 Mutsu: +3 ?? ?? 0 +4 -2? -4? -6? Nagato: -5
Mutsu: -8
??
Yamato-class 0 +3 +3 +7 0 ??
Yamato Kai Ni [3] (FBB) 0 ?? -7 ?? ?? -10
  • The table shows an estimated accuracy fit bonus based on having one fit gun equipped.
  • For married ships, the overweight penalty is generally reduced by 40%:
    • E.g. a married Kongou with a 46 cm receives -6 instead of -10,
    • Some exceptions will receive a bonus instead of a penalty on certain guns after marriage.
  • If more than one gun of the same class is used, multiply the modifier by the square root of the number of guns:
    • E.g. a Kongou with two IJN 35.6 cm equipped receives √2 x 7 = 9.89.
  • If guns from different classes are used together, add the modifiers together.
    • E.g. a Kongou with 35.6 cm and 41 cm mixed receives 7 - 5 = 2.
    • Exceptions arise where different guns of the same class give different bonuses on certain ships, notably Gangut, with what happens when combining 30.5 cm and 35.6 cm is still under investigation.

More generally, the accuracy offset can be defined with the formula:

[math]\displaystyle{ W = \sum^{\text{All Classes}} \left ( C_{k} M_{k} \sqrt{N_{k}} \right ) \% }[/math]

With:

  • [math]\displaystyle{ W }[/math] the resulting fit bonus or overweight penalty
  • [math]\displaystyle{ C_{k} }[/math] the main coefficient of the equipped gun class. Refer to the above table for the coefficients applied to each Battleship for their respective guns.
  • [math]\displaystyle{ M_{k} }[/math] the marriage coefficient for the particular gun class. Assumes a value of 0.6 if the ship is married, and if the main coefficient is negative.
  • [math]\displaystyle{ N_{k} }[/math] the number of equipped guns for that gun class.

Source: [1][2]

Native Guns

Since gun overweight penalty and fit bonuses are not yet all measured for some guns and ships, here is a list of the guns natively used/planned to be used in real life by each ship class.

  • The "Twin/Triple" mount distinction is made for convenience, triple guns being heavier than their twin counterpart.
  • Equipping ships with those guns may not always be optimal, but this should avoid most overweight penalties.
 Large Guns
Nation Class Caliber Twin Triple
Japanese Kongou-class
Fusou-class
Ise-class
35.6 cm
 
35.6cm Twin Gun Mount
 
35.6cm Twin Gun Mount (Dazzle Camouflage)
 
35.6cm Twin Gun Mount Kai
 
35.6cm Twin Gun Mount Kai Ni
 
Prototype 35.6cm Triple Gun Mount
 
35.6cm Triple Gun Mount Kai (Dazzle Camouflage)
Fusou-class Kai Ni
Ise-class Kai Ni
Nagato-class
41 cm
 
41cm Twin Gun Mount
 
41cm Twin Gun Mount Kai Ni
 
Prototype 41cm Triple Gun Mount
 
41cm Triple Gun Mount Kai
 
41cm Triple Gun Mount Kai Ni
Yamato-class 46 cm
 
Prototype 46cm Twin Gun Mount
 
46cm Triple Gun Mount
 
46cm Triple Gun Mount Kai
Yamato-class Kai Ni 51 cm
 
Prototype 51cm Twin Gun Mount
 
51cm Twin Gun Mount
 
Prototype 51cm Triple Gun Mount
US Colorado-class 40,64 cm
 
16inch Mk.I Twin Gun Mount
 
16inch Mk.V Twin Gun Mount
 
16inch Mk.VIII Twin Gun Mount Kai
North Carolina-class
South Dakota-class
 
16inch Triple Gun Mount Mk.6
 
16inch Triple Gun Mount Mk.6 + GFCS
 
16inch Triple Gun Mount Mk.6 mod.2
Iowa-class
 
16inch Triple Gun Mount Mk.7
 
16inch Triple Gun Mount Mk.7 + GFCS
British Queen Elizabeth-class 38.1 cm
 
38.1cm Mk.I Twin Gun Mount
 
38.1cm Mk.I/N Twin Gun Mount Kai
Nelson-class 40,64 cm
 
16inch Mk.I Triple Gun Mount
 
16inch Mk.I Triple Gun Mount + AFCT Kai
 
16inch Mk.I Triple Gun Mount Kai + FCR Type 284
Italian Conte di Cavour-class 30.5 cm
 
305mm/46 Twin Gun Mount
 
305mm/46 Triple Gun Mount
32 cm
 
320mm/44 Twin Gun Mount
 
320mm/44 Triple Gun Mount
Vittorio Veneto-class 38.1 cm
 
381mm/50 Triple Gun Mount
 
381mm/50 Triple Gun Mount Kai
German Bismarck-class 38 cm
 
38cm Twin Gun Mount
 
38cm Twin Gun Mount Kai
French Richelieu-class 38 cm
 
38cm Quadruple Gun Mount
 
38cm Quadruple Gun Mount Kai
 
38cm Quadruple Gun Mount Kai Deux

'"Double Twin Guns" in a Quadruple Mount.
Russian Gangut-class 30.5 cm
 
30.5cm Triple Gun Mount
 
30.5cm Triple Gun Mount Kai

Cruiser Bonuses

    Medium Guns
Gun Groups Guns
A 14 cm Single  · 14 cm Twin  · 14 cm Twin Kai 
B 15.2 cm Twin  · 15.2 cm Twin Kai  · 15.2 cm Twin Kai Ni 

Bofors 15.2 cm Twin Mod 1930  · Bofors 15 cm Twin Mk9 Mod 1938  · Bofors 15 cm Twin Mk9 Kai + Single Mk10 Kai Mod 1938 

6" Twin MkXXI 

C 15.5 cm Triple  · 15.5 cm Triple Kai 
D 6" Triple Mk16  · 6" Triple Mk16 mod2 

6" Triple MkXXIII 

152 mm/55 Triple  · 152 mm/55 Triple Kai 

E 5" Twin CD  · GFCS + 5" Twin CD 
F 20.3 cm Twin  · 20.3 cm N°2 Twin  · 20.3 cm N°3 Twin 

SKC34 20.3 cm Twin  · 203 mm/53 Twin 

G 8" Triple Mk9  · 8" Triple Mk9 mod2 

Notes:

  • Future Medium Guns may fall in one of those categories based on similarities like caliber and number of guns.

Light Cruisers (CL/CLT/CT)

Accuracy   bonuses for Light Cruisers (CL), Torpedo Cruisers (CLT), and Training Cruisers (CT).

Ships Guns group[1] Accuracy bonus/penalty
1st Gun 2nd Gun Unmarried Married
Default to
every CL(T)/CT
- - 0 0
A/B A/B 0 2
C C -5? -1?
D D -6 -3.6
E E
F F
F - -3 -1.8
G G -22 -17.6
Agano-class B - 5 7
B B 6 8
F F -8 -6
Ooyodo C C -2 -1.2
F F -10 -8
Atlanta-class E E 0 3
Abyssals - - 0[2] -
Any Medium Gun - -3[3] -
  • There is not enough data to pin down the exact fit accuracy formula.
  • Other gun combinations fits cannot be extrapolated yet.
  • There are known tests where the fit bonuses do not scale linearly with the number of guns.


Firepower   bonuses for Light Cruisers (CL), Torpedo Cruisers (CLT), and Training Cruisers (CT).

Ships 14cm Single  14cm Twin /Kai 
 
 · 15.2 cm /Kai 
 

Bofors 15.2 cm  · 6" Twin MkXXI 

CL(T)/CT +1  +2 

Sources: [3][4]

Heavy Cruisers (CA/CAV)

CA(V) as well as other "Medium Guns capable ships" are still under investigation, this information is outdated and may be erroneous.

Accuracy   bonuses for Heavy Cruisers (CA), Aviation Cruisers (CAV), as well as some other "Medium Guns capable ships" like Seaplane Tenders (AV), Kamoi (AO forms).

  • Other ships like Submarine Tenders (AS) are unmapped yet.
Ships 14cm Twin /Kai 
 
15.2 cm /Kai 
 
C IJN 20.3 cm 
 
 
203mm/53  G
Day Night
CA(V) 0 +5 +5N? 0
Mogami-class +2
Mogami-class Kai Ni +5
Zara-class +1
AV/Kamoi (AO) -6N -6N -8 -10N -8 -10N?
  • The table shows an estimated accuracy and/or firepower fit bonus based on having one fit gun equipped.
    • The variable N refers to the number of guns of that category equipped. (Ex: 2 guns of 2N = 4 ACC)
  • Bonuses from guns of different classes are simply added together.
  • The night fit bonus from the 20.3cm series used to be capped at +15%. However, it is unknown whether this cap has been removed or not from the recent updates.
  • There is a possibility that certain fit categories only work during the day. The possibility is plausible, but there's no concrete data proving. The alternative theory is that the night bonus from the 20.3cm series overrides any other categories.
  • The information in this table is sourced from these two spreadsheets (1) (2) the latter maintained by Dewy, both with the relevant sources linked in the spreadsheet.


Firepower   bonuses for Heavy Cruisers (CA), Aviation Cruisers (CAV), as well as some other "Medium Guns capable ships" like Seaplane Tenders (AV), Kamoi (AO forms).

  • Other ships like Submarine Tenders (AS) are unmapped yet.
Ships 203mm/53 
Zara-class +1

12.7 cm HA Late Models

As of 2017/06/23, Yura Kai Ni, Mutsuki-classes, and Kamikaze-classes gain accuracy   bonuses with some main Late Models High Angle 12.7 cm guns  .

Ship 12.7 cm Single HA Mount (LM)  12.7 cm Twin HA Mount (LM) 
CL(T)/CT +4N  +2 +2N
Yura Kai Ni  +4 +10N 
Mutsuki-class +5 
Kamikaze-class ??

Notes:

  • Only Yura Kai Ni  and Satsuki Kai Ni  were tested. It is unknown whether the other ships listed also receive those bonuses, or whether it only works for specific remodels.
  • The variable N refers to the number of guns of that category equipped (ex: 2 guns of 2N = 4).
  • It is unknown whether the 12.7 cm Single HA  gives any bonus.
  • The information in this table is sourced from this spreadsheet maintained by Dewy, but is lacking sources.

Destroyer Bonuses

Certain destroyers have a higher-than-expected hit rate when equipped with certain guns or sonars.

  • The bonus accuracy likely takes the form: [math]\displaystyle{ \text{ACCURACY}_\text{bonus} = \text{C} \times \sqrt{\text{N}} }[/math]
    • N being the amount of equipment.
Known "C" values
Ship/Class Gear C
Tashkent/Verniy 
 
 130mm B-13 Twin Gun Mount  5
Fletcher-class 
 
 5" Single Gun Mk.30 variants 
 
 
4[1]
John C. Butler-class  4[2]
J-class 
 
 QF 4.7inch Gun Mk.XII Kai  3
 ASDICs 
 
 
3 [3]
Mutsuki-class  12cm Single Gun Mount Kai 2  5
  1. 2x base 5" Gun  on Fletcher-class gives ~10 accuracy. This is potentially a bug.
  2. Samuel B.Roberts does not seem to receive any bonus from base 5" Gun . This is possibly a bug (maybe related to the bug on Fletcher-class).
  3. There are not enough samples on more than one ASDICs 
     
     
    sonar so it is not clear how does the accuracy bonus scales. This bonus can stack with the accuracy bonus from QF 4.7inch Gun Mk.XII Kai .

Source: [5][6]

See Also

Main data sources :