Module Stacking and Speed Modules

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Module stacking penalties apply to nearly every beneficial module you can fit on your ship, with very few exceptions.

This guide aims to help you wade through the math involved in module stacking, using speed modules as a practical example. Speed module stacking is of particular interest to anyone piloting speed-tanked ('nano') ships, but the general principles have wider applications for fitting generally. See Stacking_penalties as well.


Stacking Penalties

Everyone is probably familiar with the basic fitting rule that:

  • If the number of modules you have that affect a single attribute is less than 3 that is perfectly acceptable.
  • But if the number of modules you have that affect a single attribute is more than 3 you are doing something wrong.

But where does that come from?

Well mathfolks have sat down and figured this out (shamelessly stolen from Grismar's wiki):

  • S(n) = 0.5^(((n-1) / 2.22292081) ^2)

Where S(n) is the stacking penalty of module n. So expanding on that a little bit:

1st mod: 1.00
2nd mod: .8691
3rd mod: .5706
4th mod: .2830
5th mod: .1060

This modifier is applied in order from the highest bonus to the lowest bonus.

So as an example:

We have 3 modules that add 20%, 15% and 10% to your speed, respectively. You would get 100% of the benefits from the 20% speed mod, 87% of the 15% speed mod and 57% of the 10% speed module. Overall this is applied in the following fashion:

(1+0.2)(1+0.8691*0.15)(1+0.5706*0.1)*(base speed) or 1.48*(Base speed)

So back to the basic fitting rules up and why they exist. Its clear when looking at the above table that after 3 modules the modifier really starts to add up, after 5 modules you're getting less than 10% effectiveness out of your worst module.

  • Shield resist mods incure this penalty for the specific damage resisted when used in conjunction with Invulnerablity Fields.

Though in certain cases it's not bad to fit a fourth mod. These certain cases need to satisfy two requirements:

  • First, you have nothing better to fit (this happens on occasion)
  • Second, you're dealing with big numbers (a 5% boost to 1000 is probably a lot more significant than a 5% boost to 100)

Speed Modules

So now that we've set up some of the math lets apply this to the speed modules. These are all post speed re-balance so you old vets take note there were some changes. Namely every module now only effects speed and agility, mass is no longer in the equation in relation to the speed modules. However plates still do add mass which ties into both speed and agility.

Here's the list of all the T2 lowslot modules and T1 rigs (T2 rigs are very rarely used because they're hilariously expensive):

Module Abbreviation Speed Bonus Agility Bonus Bad Stuff
T2 Overdrive OD 12.5% 0 -20% cargo space
T2 I-Stabs IS 0 20% +11% sig radius
T2 Nanofiber NF 9.4% 15.8% -20% hull hp
Aux Thruster rig AT 7.25% 0% -10% armor hp
Polycarbon rig PC 5.5% 8.1% -10% armor hp
Low Friction Nozzle rig LF 0 11.7% -10% armor hp

So one thing you'll probably notice is that rigs are completely outclassed by all low slot modules. Rigs provide just over half the bonus of their corresponding lowslot module. Compound the lower bonus with stacking penalties and, if you fit more than two lowslot modules, rigs are essentially acting as fourth order stacked lowslot modules, and going back to the rules we all grew up with more than three modules giving bonuses to the same thing is generally bad.

To clarify that point, you probably shouldn't bother rigging if its going to be stacking with two or more lowslot modules (unless we're dealing with really big numbers and have nothing better to fit).

Combinations of Modules Including Stacking

Two lowslot modules

Combination Speed Bonus Agility Bonus
2 OD 24.7% 0
1 OD 1 NF 21.7% 15.8%
2 NF 18.3% 27.4%
1 OD 1 IS 12.5% 20%
1 IS 1 NF 9.4% 31%
2 IS 0 33.9%

Three lowslot modules

Combination Speed Bonus Agility Bonus
3 OD 33.6% 0
2 OD 1 NF 31.4% 15.8%
1 OD 2 NF 28.2% 27.4%
2 OD 1 IS 24.7% 20%
3 NF 24.7% 33.9%
1 OD 1 IS 1 NF 21.7% 31%
1 OD 2 IS 12.5% 33.9%
3 IS 0 41.5%

Combinations of Rigs Including Stacking

Two rigs

Combination Speed Bonus Agility Bonus
2 AT 14.5% 0
1 AT 1 PC 12.6% 8.1%
2 PC 10.5% 14.6%
1 AT 1 LF 7.5% 11.7%
1 IS 1 PC 5.5% 17.9%
2 LF 0 20.7%

Three rigs

Combination Speed Bonus Agility Bonus
3 AT 19.4% 0
2 AT 1 PC 18.1% 8.1%
1 AT 2 PC 16.2% 14.6%
2 AT 1 LF 14.5% 11.7%
3 PC 14% 18.5%
1 AT 2 LF 7.5% 20.7%
3 LF 0 26%

Combinations of Lowslot Modules and Rigs Including Stacking

TODO: Will add at a later time.


For optimal speed and agility its advisable to maximize your use of nanofibers and polycarbs. The reason is obvious when you look at the various combinations posted. The only exception to this is when your tank only involves a Damage Control.

If you're planning on combining both lowslot modules and rigs be sure to consider the fourth order stacking penalties.

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