Combat/Overweight Penalty and Fit Gun Bonus

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.
  • 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.

Such fit mechanics do not apply to abyssals.[1]

Large Caliber Main Guns

Battleships receive accuracy bonuses if the guns are fit and accuracy penalties if its overweight[1]. How much bonus/penalty a ship receives, depends on the battleship class, the caliber and type of the gun, and whether the battle takes place during day or night.

Ship Class (P )35.6cm (DC ),
38cm (K ),
30.5cm (K ),
38.1cm  (/N )
38cmQ ,
38cmQK 
381mm ,
381mmK 
41cm 16inch (United States Navy) 16inch (Royal Navy) 46cm P51cm ,
51cm 
41cm ,
Proto ,
Kai 
3K2  2K2  Mk.7  Mk.7
+GFCS
 
Mk.6
mod.2
 
Mk.I  +AFCT  Kai
+FCR
 
Proto  46cm  Kai 
Gangut  +7
30.5cm: +10
0 +1 -7 -3 -9~10? ?? ?? -7 -18 ?? N/A
Kongou-class 
 
 
 
+7 0 -2 -5 -5? -5 -6~7? -5 -6 -3 -7 -10 -10?
Bismarck 
Vittorio Veneto-class 
 
+4 0? +1 -5 -5 -4? -5 ?? ?? -7 -10 ??
Iowa  +4? 0? -2? -5 0 +2 -7 -10 ??
South Dakota  -5
M: +4.6
Richelieu  +4 +4~5 -2 -5 -5 -7 -14? -8 -7 -10 ??
Warspite  +6
38.1cm: +8
+1~2 +2 -2? +5 ?? +3~4 -8 -11 ??
Nelson  0 0 +3? 0 0
Ise-class Kai/Fusou-class Kai/Ni 
 
 
 
 
 
+4 0 +2 +2 0 0? -3 -7
F+: -11?
-4?
Ise-class Kai Ni 
 
+4? 0? +4? +4? +6 +2 ?? -7
F+: -11?
??
Ise/Fusou-classes Base 
 
 
 
+2 0? +2 +2 +2 +2? +3 -3 -7 ??
Nagato-class 
 
0
Nagato-class Kai Ni 
 
+2? 0? +2? +5 +5 +5~6 0 +4 -2? -4? -6? Nagato: -5
Mutsu: -8
Yamato-class 
 
0 +3 +3 +7 0
Note: Fit gun mechanics are still being investigated to this day, hence the values are not final and may be subject to changes. Values with a question mark either mean that it is not conclusive yet or the conclusion drawn here is not the same as the one drawn by Yumeji.
  • The table shows an estimated accuracy fit bonus based on having one fit gun equipped.
  • For married ships, the overweight penalty is reduced by 40% (A married Kongou with a 46cm receives a penalty of -6 instead of -10, for example).
  • If more than one gun of the same class is used, multiply the modifier by the square root of number of guns. (A Kongou-class with two A class guns equipped for example, that's √2 x 7 = 9.89)
  • If guns from different classes are used together, add the modifiers together. (A Kongou with a 35.6cm and 41cm mixed for example, that's 7 - 5 = 2.
  • Exceptions arise where different guns of the same class give different bonuses on certain ships, notably Gangut. What would happen if you combine 30.5cm and 35.6cm is still under investigation.
  • The information in this table is sourced from this spreadsheet maintained by Dewy with the relevant sources linked in the spreadsheet.
Last Updated: Aug 24th 2020 Made by: Tsubakura

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]

Where:

  • [math]\displaystyle{ W }[/math] is the resulting fit bonus or overweight penalty
  • [math]\displaystyle{ C_{k} }[/math] is 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] is 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] is the number of equipped guns for that gun class.

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/planed 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

Medium Caliber Main Guns

Cruisers can receive accuracy and/or firepower bonuses from using fit guns in their load-out.

Ship Class 14cm Single 
15.2cm Single  ( )
14cm Twin 
 14cm Twin Kai 
15.2cm 
15.2cmK 
Bofors 15.2cm  15.5cm 
 15.5cmK 
20.3cm 
 20.3cm(2) 
20.3cm(3) 
203mm/53  8inch Mk.9 
 8inch Mk.9 m.2 
Day Night
CL(T) +4N  +1  ?? +2?  +2  +3  ??  -2 -2N  -3N? [1] -2 -2.5N?  -10N? 
Agano-class 
 
 
 
?? +5 +2N?  +2  -2 -2N 
Ooyodo  ?? +2?  +2  +2 
CA(V) 0 +5 +5N?  0
Mogami-class 
 
 
 
+2 
Mogami-class Kai Ni 
 
 
+5 
Zara-class 
 
+1  +1 
Seaplane Tenders (AV) -6N  -6N  -8 -10N  -8 -10N? 

Note: Fit gun mechanics are still being investigated to this day, hence the values are not final and may be subject to changes. Values with a question mark mean that it is potentially outdated and might no longer be correct.

  • 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.
  • As of 13th December 2018 the hidden firepower bonus of 14cm Twin Gun Mount Kai  does not work/does not exist[citation needed].
Last Updated: June 23rd 2019 Made by: Tsubakura

Small Caliber Main Guns

As of 2017/06/23, Yura and Mutsuki/Kamikaze-class destroyers gain bonuses with some main HA guns  .

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

Unknown factors:

  • Only Yura K2  and Satsuki K2  were tested[citation needed]. It's unknown whether the other ships in the same class would receive the same bonus 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 ACC).
  • It is unknown whether the 12.7 cm Single HA Mount  gives a fit bonus or not.
  • The information in this table is sourced from this spreadsheet maintained by Dewy, but has no sources linked in the spreadsheet.
Last Updated: December 5th 2018 Made by: Tsubakura

DD Fit Accuracy

Certain DDs 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 Mount Mk.30 variants 
 
 
4[1]
John C. Butler-class   5" Single Gun Mount Mk.30 variants 
 
 
4[2]
J-class 
 
 QF 4.7inch Gun Mk.XII Kai  3
 ASDICs 
 
 
3 [3]
Mutsuki-class  
  
  
  
  
 
 12cm Single Gun Mount Kai 2  5
Source: [1][2]
  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 .

See Also

Fit gun bonus - Reddit intermediate players' guide