Stacking Penalty

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Part of a series on
Skills and Fitting



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Fitting Skills · Support Skills
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Advanced Fitting Info

Passive Tanking
Stacking Penalty

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Post RMR Stacking Penalty

Important links

1) Excellent eve-o post explaining the whole topic with clear examples: <-- Totally awesome, should be compulsory reading for newbies

2) The math explained (technical version):

3) Very useful stacking calculator:


The stacking penalty for the nth module is


where a is equal to 0.8691199806, which can be taken as 0.87 for most purposes.

The first module will have full effect, the second 87%, the third 57%, the fourth 28%, and so on.

Further details & shield HP calculations

(See the eve-o thread for comprehensive details; the following will be updated soon.)

Note that the important column in the above table is the Effectiveness one - the Multiplier column is just a result derived for this particular sensor dampening case. Any attributes in the game which the Effectiveness values apply to are called stacking-nerfed. (Attributes which are not stacking-nerfed can be directly multiplied to obtain the final effect - for example, 3 PDS Is gives a final shield hp of 1.04^3 = 1.12486 = 112.5% the original hp.)

You can calculate the incremental effectiveness of successive modules by simply multiplying the effect with the corresponding Effectiveness value. For example, if you have 2 Invuln Fields on your ship already, putting on a 3rd Invuln Field will give a further resistance bonus of 25% x 0.57 = 14.25% instead of the usual 25%. (0.57 is the Effectiveness factor from the table (WHICH HAS BEEN DELETED) for the 3rd stacked mod.)

To calculate your final shield hp bonus as a result of this 14.25% resistance bonus, simply calculate 1 / (1 - 0.1425) = 1.166, i.e. you get a total effective shield hp of 116.6% from adding the 3rd Invuln Field. This formula can be applied to any kind of resistance and allows you to calculate whether adding a shield extender (gives a fixed additional hp amount) or hardener (gives a percentage additional hp amount) is better.

Finally, if calculating by hand, note that bonuses always apply from the largest to the smallest. The largest effect would have Effectiveness value 1.0, the next largest 0.87, the third 0.57, and so forth. - Neko Kekko

Stacking-nerfed attributes

(taken from link 2)

List of attributes that are certainly stacking-nerfed:

  • max targeting range
  • sensor resolution
  • each of the shield/armor resists
  • damage mod for weapons
  • rate of fire mod for weapons
  • turret tracking and optimal range
  • shield booster boost amount modifier
  • propulsion upgrades (overdrives, nanos, istabs and the corresponding rigs, the signature radius bonus from istabs too!)

List of attributes that are NOT stacking-nerfed:

  • ship speed
  • cargo capacity
  • shield/armor/structure hitpoints
  • recharge rates for capacitor/shields
  • powergrid and CPU output of ship


"Rigs get stacking-nerfed together with modules that affect the same attribute." - Akita T (from link 2)

As of 4th June 2008 [Turret Class] Locus Rigs (bonus to optimal range) are not affected by a stacking penalty. This was change about six months later and Locus Rigs are currently stacking penalized.