Fitting ships

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	EVE University offers classes on:
Fitting (CORE class) Ship Roles (CORE class)

The fitting of ships refers to both the process of selecting which modules, rigs, ammunition, drones, etc. should be used with it for it to be able to do what the player wants it to, and to the act of then actually assembling a ship hull and placing the above-mentioned items in it so that the ship becomes ready to be undocked and used.

There are no strict rules that you must follow when fitting a ship; these guidelines are designed to help you until you know when you can ignore them. Ship fitting is a wide-ranging topic, and players may wish to come back to both the foundational principles as well as more detailed considerations as they gain familiarity with it. Good sources of more advanced information on ship fitting that go beyond the scope of a general article on it are also third-party sites that host information pages dedicated to specific areas of gameplay.

Assembling a fit

Here are some tips for buying and assembling your fit:

• Use the ship simulator: From the fitting window of any ship in EVE (even ones you don't own) you can start simulating a fit, and see how the ship's stats change with different modules. You can then conveniently buy the whole fit from the market.

• Consider buying at trade hubs; they are more likely to have all the parts you need.

Fitting skills

Main article: Fitting skills

Fitting skills reduce the CPU or powergrid requirements of modules or just give you more raw CPU or powergrid to play with. Having decent fitting skills is very useful. Very good fitting skills really help you to fit T2 modules and weapons, which demand more CPU and powergrid than their T1 equivalents, and to fit T2 ships, which often have tight powergrid and CPU. Levels in these skills are often required to fit useful modules, too.

(Note that Hull Upgrades doesn't make basic fitting easier, even though it has 'Upgrades' in its name. It gives a pilot 5% more armor per level, and Hull Upgrades at Lvl 5 is required to fit a Tech 2 armor tank.)

Tip: The benefits of CPU Management and Power Grid Management apply to the whole ship. Skill point for skill point, they provide significantly more fitting benefit than the module-specific skills. You can't go wrong training these two skills to level V as soon as is practical.

General theory

Fit for a purpose

Generally, the more tasks you want a fit to do, the worse it performs at each particular task. Some ships have very specific uses: a Venture mining frigate is not very helpful in either PvE or PvP combat.

But even a combat ship will almost certainly need different fits for PvE and PvP, because, for example, in PvP, you usually receive a lot more damage in a much more limited time than in PvE, and enemy players, unlike NPCs, need to be prevented from warping away. Even within PvP, the same ship can have one fit for close-range brawling in a small gang and a completely different fit for fighting at longer ranges in a large fleet.

Of course, there are dangers in over-specialization too, especially when you're not working with other players. If you're going to exploit a low-class wormhole while solo you want your ship to deal and tank damage, launch probes, and maybe cloak so that you can hide if you see a gang of enemies on your directional scanner. Strategic Cruisers and, to some extent, Tactical Destroyers are specifically designed to be flexible multitask ships.

Some useful aspects of a fit's design to consider in thinking about its purpose are:

• Engagement Range: if it is a combat fit, at what range do you want the fit to fight?
  • Brawling (<15km)
  • Kiting (15–30km, that is, within warp disruption range, which will vary depending on the hull and the presence or absence of bursts affecting this)
  • Skirmishing (30–100km)
  • Sniping (100km+)
• Role: what will your fit do on the battlefield?
  • Primary damage dealer ("DD")
  • Tackler
  • Scout
  • Logistics
  • Electronic warfare
  • Screen (holding hostile tackle or DD ships away from the core of a friendly gang)
• Tank: how will your fit avoid or counter incoming damage?
  • Buffer armor tank
  • Active armor tank
  • Buffer shield tank
  • Passive shield tank
  • Active shield tank
  • Speed tank
  • Range tank (there are very few situations where you want no tank!)
  • Will the damage type be predictable? For instance, PvP against Amarr laser ships and PvE combat in missions, Incursions, and combat sites can involve highly predictable damage types which can be accounted for in advance.
• Environment: where will your fit operate?
  • High security space: collateral damage will be risky
  • Low security space: gate and station guns are a risk for any aggressor
  • Null security space: bubbles might be used, as might bombs; accessible stations/structures might be rare
    • ESS grids: only some hull sizes can enter, microwarpdrives and micro jump drives won't function, and warping will be impossible
  • Wormhole space/Pochven: intel will be more limited; basic probing capabilities might come in handy
  • Abyssal Deadspace: only some hull sizes can enter; damage types will be unpredictable; environmental conditions will affect the ship

For all kinds of fit, for all kinds of purposes, ask yourself what level of risk will you expose this fit to? A fit used for highly predictable PvE combat or for mining in relatively secure space can be more expensive than one used for one-way filament PvP trips to hostile nullsec space--though even in the safest kinds of environment you must never fly what you can't afford to lose.

Consider a ship's bonuses

Every ship comes with per-level bonuses, which often point toward the uses that the ship was designed for.

The Caldari Blackbird, for example, gets a 15% bonus to ECM Target Jammer strength and a 12.5% bonus to ECM Target Jammer optimal range and falloff for each level its pilot has in the Caldari Cruiser skill. These bonuses suggest that it's best fitted as an electronic warfare platform that fights well at long range.

Sometimes it's okay not to take advantage of a ship's bonuses: although the Brutix is bonused to give a more efficient active armor tank, it is frequently seen with a buffer tank, and quite often a shield tank at that. This is because the ship has the ability to supply a huge amount of DPS with its six damage bonused blasters and a shield tank leaves the lowslots free for damage upgrades to squeeze out even more damage.

Don't mix tanks

If you're going to tank, either shield tank or armor tank. Don't both shield and armor tank in the same fit.

Most of the time, a tank takes up a substantial proportion of your powergrid, your CPU, and either your midslots (for a shield tank) or your lowslots (armor tank). If you fit a shield tank, you can put useful things (damage modules, speed and agility modules, etc.) in your lowslots; if you armor tank, you can put useful things (tackling modules, electronic warfare modules, propulsion modules, etc.) in your midslots. Utilizing both types of tank at once leaves you with little space for other useful modules.

Furthermore, fitting Shield Extenders and Shield Rigs increases Signature Radius, and fitting Armor Plates and Armor Rigs reduces your speed, both of which will cause you to get hit more and harder, thus burning through your hitpoints faster.

This rule also applies to mixing buffer tank with active tank: these modules both require heavy powergrid and CPU, both consume the same limited set of slots, and both fitting theories satisfy different—usually mutually exclusive—goals and conditions.

The above two options are not the only ones, but the vast majority of widely used fits use either a shield or armor tank. Double-tanked ships are usually only used as bait, or with a small subset of hulls for 1v1 fights (most prominently the Breacher). Hull-tanking is a strategy that is sometimes fielded to great effect in solo and small-gang PvP.

Don't mix guns

If you have a rack of exactly identical guns on your ship, they will all have precisely the same optimal and falloff ranges and exactly the same tracking. This means you only have to worry about getting your ship to one ideal range and keeping the enemy's angular velocity below one value.

Furthermore, you can group identical weapons so that they can all be activated or reloaded or unloaded at once, which reduces the micromanagement required in combat. Grouping isn't always the best option, especially if you learn to overheat your guns using the Thermodynamics skill, but it's a good way to start.

Missiles are a little different because they aren't affected by tracking and have a simpler kind of range, but the same principle often applies to them. Note that "don't mix guns" doesn't mean you shouldn't put missile launchers in extra highslots if all your turret hardpoints are full and you want more DPS (as in, for example, a Stabber with four autocannons and two missile launchers). Remember, though, that there are other options worth considering for spare highslots, such as energy neutralisers/nosferatus, salvagers, tractor beams, remote repair modules and drone link augmentors.

There are exceptions to this principle, such as in dreadnought ratting, but they are extremely narrow and limited exceptions unlikely to apply to new players.

Bigger guns aren't necessarily better

In EVE, small ships can sometimes outfly larger ships with, on paper, much higher potential damage outputs. A similar principle applies to some aspects of fitting, especially weapon fitting. Bigger guns do more DPS, assuming they hit, but they track targets more slowly and they use up more powergrid and CPU.

So, for example, there are three kinds of medium-sized autocannon: Dual 180mm, 220mm, and 425mm. The 425mm autocannons do a bit more damage, but the 220mm autocannons have much more forgiving fitting requirements (especially if your fitting skills -- see below -- need more training). On some ships, it may be that fitting a rack of 425s would use up so much powergrid and CPU that you wouldn't be able to fit a tank. In that situation, fitting 220s would be better because, even though you would do a little less damage per second, your ship would survive longer and so would probably apply more total damage.

This does not mean that you should fit frigate-sized guns on a cruiser. Downsizing within the available medium or large guns is sometimes wise, but downsizing from large to medium guns, or from mediums to smalls, usually isn't, unless you're fitting a bait ship or certain kinds of drone boat fits.

Steal other people's ideas

EVE University has two ship loadout forums, where pilots can get comments on their fitting ideas. They have some threads with suggested fits. It's also worth searching the forums for past threads if you're interested in a particular ship. The #fitting-chat Discord channel should be the first place new players look for fits, and ask for advice. This forum is not publicly available.

The wiki also has a page for each ship in EVE (e.g. Atron). These pages often have at least a few notes on basic approaches to fitting the ship.

You can also get advice in the University's chat channels or on the EVE Uni Discord. To link a fit that you have set up already into in-game chat, drag the ship's name from the fitting window and drop it into the chat entry box; to link one from the fittings browsing window, drag the image of the ship.)

The subreddit devoted to EVE ship fitting, r/fittings has active discussions of ship fittings and posts asking for suggested fits for specific play styles and ships. The material here varies in quality.

zkillboard.com shows you how people fit their ships in actual fights. Not everybody fits their ship smartly, of course, but if you can find players who are successfully doing what you want to do and identify their successful fits from their losses, you can often learn something. See this guide to make the most of zkillboard.

Don't overuse fitting modules

There are some low-slot modules and rigs which increase your powergrid or CPU, and so are sometimes called "fitting modules". See below for how to decide on which fitting module to use.

It is sometimes necessary to use a fitting module or a fitting rig, but if you have a fit that requires more than one it's often a bad sign, and it may mean that you need better fitting skills, or are trying to fit too ambitiously. If you give up two or three slots for modules and rigs just to mount the rest of the fit on the ship, you will lose a lot of potential utility.

Like most of the other principles here, more experienced players can bend or break this for specialized reasons, but it's an excellent rule of thumb for new players.

Ship simulation tools

EVE includes a limited fit simulation tool, but you can also use more powerful third-party tools to try fits outside the game.

The most popular tool in EVE University is PYFA. You can load your character's specific skill profile into Pyfa and see how a particular fitting would fly and fight with your character piloting it. Pyfa can even simulate the effects of different types of ammunition, overheating, drugs, command bursts, and incoming damage. Fits can be exported from Pyfa to the clipboard and then from the clipboard straight into your in-game fit library.

Fit simulations are theory, of course, and don't always work out exactly as planned in practice: autocannon, for example, almost never deal their on-paper Pyfa DPS, because they are almost always operating in falloff range. For any especially high-stakes or experimental fits, consider gathering a few friends to help and trying them out on the test server, Singularity.

Choosing modules (PvP)

Once you have selected the engagement range, role, and tank of your ship, comes the time to actually fit it. The following remarks are primarily PvP-oriented, though some are also useful considerations for PvE.

Weapons

For ships where damage is the primary purpose, start with weapons that are consistent with your engagement range and ship class: laser beams for snipers, artillery for skirmishers, blasters or rockets for brawlers etc. Try to use the most damaging weapons of the class that you've selected. You may have to downgrade them later (or may choose to downgrade them later so that everything will fit, or to improve tracking), but for now, if you're fitting blasters, try to fit neutron blasters, and so on.

Do not mix weapons and stick to weapons that go with your ship's bonuses. In addition, fit as many weapons as your ship has either missile or gun hard-points. As discussed above, do not mix different weapons, e.g. 220mm and 425mm autocannon.

In a similar fashion, if the ship is designed to act as a logistics ship, the first thing to do is to fit the remote repair modules. If you are fitting an EWAR ship, start by fitting the EWAR modules that match your ship bonuses. If you are fitting a tackling ship, fit the propulsion and the tackle modules.

Role-enhancing modules

Now look at your ship's role. If your role is damage, you're probably already in good shape, but start to consider tracking and range. If you are going to be shield tanking, by default you should be using two damage-increasing modules consistent with your weapons in the lows. You might end up with one, you might end up with three. But start with two. If you have more than four low slots and will be using guns, you'll probably want to fit at least one Tracking Enhancer module as well. If you are going to be armor tanking, by default you should have one damage-increasing module consistent with your weapons in the lows.

This also applies to ECM ships: if you are shield-tanking, try fitting two Signal Distortion Amplifiers. If you are armor-tanking, try to find room for one. This is generally a good rule of thumb for enhancing the damage or the other effects that your ship puts out.

Finally, armor-tanking turret-using ships with lots of mid-slots should consider a Tracking Computer in one or perhaps two of them.

Nearly all PvP ships should give a single mid slot over to a propulsion module, something to increase your ship's speed. You must choose between a Microwarpdrive (MWD) or Afterburner (AB). An MWD allows greater maneuverability which makes them more commonly fit. However, MWDs bloom your ship's signature radius (making you an easier target) and are disabled by warp scramblers. ABs are popular on brawling armor ships, as they enable a signature tank against larger opponents and cannot be shut off by the warp scramblers used at close ranges.

Most PvP ships should give a single mid slot to a tackle module of some type. For skirmishers (specialized scouts), primary damage, and screening ships this should nearly always be a "long point", a Warp Disruptor of some kind. Ships in a tackle role should usually fit a Warp Scrambler module of some kind. Some types of scout and initial tackle might want to try fitting both a point and a scram. Ships in other roles in larger fleets can forgo tackle modules. In a small gang it is often desirable to have a tackle module on almost every ship. Space permitting, a web is desirable on close-range damage dealers. Stasis Webifiers do not hold the target on grid as points and scrams do, but they slow the target down, hampering kiters and helping your tracking and missile hits.

ECM is a big danger to logistics, so logistics pilots should consider fitting ECCM to counter it. A sensor booster (either to counter sensor dampening or to allow your to apply reps faster) should also be considered.

Tank

Next, consider your tank. First, fit a Damage Control unit of some kind. T2 Damage Controls should always be favored, but meta 3 or 4 can sometimes be chosen due to dramatically less CPU usage (bear in mind that meta 4 damage controls are quite costly). If fitting an Assault Frigate or Heavy Assault Cruiser, use an Assault Damage Control instead.

Buffer armor tanks use between two (generally for T1 frigates) and six (generally for battleships or logistics) low slots. In order, fit the following:

• the heaviest armor plate your ship can fit consistent with its size and your guns (i.e. 200 or 400mm for frigates and destroyers, 800 or 1600mm for cruisers, 1600mm for battlecruisers and battleships). You should fit T2 if you can, downgrading to meta 4 otherwise.
• A Multispectrum Energized Membrane (MEM, formerly known as an EANM), T2 if you can
• A second T2 MEM, or a Multispectrum Coating (formerly known as an ANP) if it won't fit
  • NB: A T2 Coating is both easier to fit and gives better bonuses than a meta MEM
• look at your four armor resistances and "close" the one that is lowest with a single active armor hardener of the appropriate type
• if you are flying a battleship, consider adding a second plate.
• either add a 3rd MEM, or a reactive armor hardener; alternatively, consider removing both MEMs and fitting 3 active hardeners of your lowest resists

Remember that on DD ships you want to leave room for at least one damage module (e.g. magnetic field stabilizer for hybrids), and often two.

Buffer shield tanks operate in a very similar fashion but with one fewer slot, using between two and five. In order, fit the following:

• a Large Shield Extender (for cruisers and larger) or a Medium Shield Extender (for frigates and destroyers).
• one Multispectrum Shield Hardener, or if cap is an issue (and you are only using two slots) possibly a second shield extender of the same type
• look at your four shield resistances and "close" the one that is lowest with a single active shield hardener of the appropriate type
• a second Multispectrum Shield Hardener
• if you have the power grid for it, a second Large Shield Extender

Active armor tanks operate in a similar fashion but generally replace the plates with Armor Repair Modules plus one Ancillary Armor Repair module of the appropriate size. They may also replace MEMs with a second (and sometimes even third!) armor repairer. Active shield tanks replace the Shield Extenders with one or perhaps two Shield Boosters, the first of which is usually an X-Large Ancillary Shield Booster (cruisers and up) or Medium Ancillary Shield Booster (frigates). Use caution if intending to fit a Large Ancillary Shield Booster. In most applications, it will not repair sufficient damage to be useful.

Passive shield tanking is not normally used for PvP because the incoming damage in PvP is usually higher than a passive shield recharge rate can keep up with, even when enhanced by modules and ship bonuses.

Fitting modules

At this point, you are possibly running out of power grid, CPU, or both. It is at this point that you begin to have to consider using "fitting mods." Fitting mods operate by closing the gaps in your fit to allow everything you want to use to fit on the ship. In general, you should try not to use fitting mods unless the fit absolutely demands it. The six most common fitting mods are:

• Ancillary Current Router rig
• Power Diagnostic System low slot module
• Reactor Control Unit low slot module
• Micro Auxiliary Power Core (MAPC) low slot module.
• Co-Processor low slot module
• Processor Overclocking Unit rig

The first four increase your power grid; the MAPC is for greatly increasing grid on frigates--it is common on shield tanked frigates--and the RCU is for greatly increasing grid on ships bigger than frigates. The last two increase your CPU.

In general, try to use the rig first before sacrificing a valuable low-slot module. Under almost no circumstances is fitting more than two fitting mods a good choice. If you find yourself fitting more than two fitting mods, you have probably made an incorrect choice in your ship fit somewhere. Fit meta 4 shield extenders or plates; reduce the number of shield extenders or plates; or reduce the guns you have chosen by one grade, from (for instance) neutron blasters to ion blasters, or from 425mm autocannons to 220mm autocannons.

As you adjust the fit of your ship, do not be afraid to change some of the modules from T2 to meta modules, usually meta 4 modules. This most often applies to Shield Extenders, your Damage Control, your point or scram, and your afterburner if not already meta (microwarpdives should never be T2). These changes will give you back a couple of percent of power grid or CPU here and there and are often all that's needed to bring a fit into line if the fit is close. It is usually not a good idea to change your resistance modules for meta modules; they are far less effective than T2 modules.

Speed tanking

Speed-tanking operates in a similar fashion but reduces the maximum number of tanking modules available to one or two, usually focusing on shield. Most often, a Medium Shield Extender (often of the meta variety) and a Damage Control module are the two modules chosen. Alternately, other ships work well with two Large Shield Extenders and a Damage Control. In general, if you have only a few tanking modules on a ship, it is better to increase buffer with those that you do use unless you are also flying with a logistics ship, in which case you can replace one with a single module to increase your resists.

Final slots

At this point, you may have a low slot or two free. You may have a mid slot or two free. And you may have a high slot or two free.

High slots are the easiest, and the only ones you should consider leaving empty (due to high fitting requirements of the options). For ships in a tackle role, a NOS is usually the best choice. For ships in all other roles, a neut is usually the best choice. Remember to intersperse your utility highslot modules or your empty highslots between your weapons, to absorb heat damage when overheating.

A free low slot should be given to an additional damage module, an additional Tracking Enhancer, or (if you're running short of CPU), a Nanofiber Internal Structure. An additional mid slot should be given to an additional tackle mod (usually a Stasis Webifier), a Capacitor Booster, or some form of utility electronic warfare, usually a Sensor Dampener.

Inertia Stabilizers should not be fit on PvP ships under any circumstances. Sensor Boosters can be fit on PvP ships but should be fit only with a great deal of care and consideration; the most common use-case is for gate camping. In a gang, this module will nearly always draw derision unless it is specifically required for sniping applications or the like.

Finally, modules that passively regenerate some aspect of your ship's operation should almost never be used in PvP. These include Cap Rechargers, Cap Power Relays, Shield Rechargers, and Shield Power Relays. While these modules are fine for PvE, the incoming damage or capacitor costs in PvP will generally be too strong for these modules to have much if any effect.

Rigs

Finally and last, rig your ship using any remaining rig slots. In general, at the basic level, buffer shield tanking ships should use a full set of Core Defense Field Extender rigs. Passive armor ships should use a full set of Trimark Armor Pumps. This will increase the size of your ship's buffer and extend your life on the battlefield. Active tanking ships use more specialized rigs. Active armor-tanking ships can use two Auxiliary Nano Pump rigs and one Nanobot Accelerator rig. Active shield-tanking ships can give one or two rig slots over to increasing shield resistances but may also use a Core Defense Operational Solidifier or (much more rarely) a Core Defense Capacitor Safeguard. Of course, if you have given over some rig slots to fitting rigs, you will have fewer rigs to devote to defense.

As with passive regeneration modules, do not use the Core Defense Field Purger rig in PvP at the basic level. While there are advanced level ships that can (and do) use this rig successfully in PvP, newer players should stick with increasing buffer.

Fitting math

In EVE, there are two types of modifiers.

1. Flat modifiers are added directly to whatever stat they affect. For example, 1600mm Steel Plates I increases armor by 3500.
2. Percent modifiers multiply the stat they affect. For example, Hull Upgrades IV gives a 20% bonus to armor (or, more precisely, multiplies armor by 1.2).

Basic bonuses

Two 25% bonus give a 56% bonus. Two 50% bonuses give a 125% bonus. More bonuses are generally better than one big bonus. Best is lots of big bonuses.

When percent modifiers combine, they multiply by each other. For example, Hull Upgrades IV gives +20% armor and a Layered Plating II module gives +8% armor. This doesn't give +28% armor, but instead:

[math]\displaystyle 20\% + 8\% + (20\% \text{ of } 8\% ) = 29.6\% [/math]

As noted above, percentages are really just multipliers. For example, +20% is a 1.2 multiplier, and +8% is a 1.08 multiplier. This changes the above formula into:

[math]\displaystyle 1.2 \times 1.08 = 1.296 [/math]

As an example, lets take a look at the Harbinger with a 1600mm Steel Plates I, Hull Upgrades IV and a Layered Plating II. The base armor for the Harbinger is 5250. The plate gives 3500 more armor and, as we saw above, Hull Upgrades IV gives a 1.2 multiplier and layered plating a 1.08 multiplier.

[math]\displaystyle Total\ Armor = (5,250 + 3,500) \times 1.2 × 1.08 = 8,750 × 1.296 = 11,340[/math]

So the Harbinger will end up with 11,340 HP of armor.

Basic reductions

Some reductions are actually bonuses. Two 25% reductions make a 44% reduction. Two 50% reductions make a 75% reduction. One big reduction is better than lots of small ones.

Again, like bonuses, reductions are best thought of as multipliers. For example, a 25% reduction is a 0.75 multiplier.

Stacking penalties

Main article: Stacking penalties

Stacking Penalties, also known as diminishing returns, keeps players from applying many bonuses to the same stat. Stacking penalties apply only to modules and rigs. Skills and Ship Bonuses/Penalties always have full effect.

The biggest modifier from a module always gives its full effect to a stat; the next-biggest modifier has a somewhat reduced effect; the third-biggest modifier has a greatly reduced effect, and so on:

• 1st = Fully effective (100%)
• 2nd ≈ 87% effectiveness
• 3rd ≈ 57% effectiveness
• 4th ≈ 28% effectiveness
• 5th ≈ 10% effectiveness
• 6th ≈ 3% effectiveness

These are described by the following function, where n is 1 for the first module, 2 for the second module, etc.:

[math]\displaystyle Effectiveness = 0.5 ^ {( 0.45 \times (n - 1 ) ) ^ 2 } [/math]

This effect means that it usually doesn't make sense to fit more than three modules that improve any one attribute. For example, a Ballistic Control System I increases missile damage by 7%. The first module fit to a ship gives the full bonus, but the second will only give an additional 7% × 87% = 6.1% bonus, the third 7% × 57% = 4.0%, and the fourth 7% × 28% = 2.0%.

As the biggest modifiers take the smallest stacking penalties, this means that even if a large number of people have a Remote Sensor Booster I on a target, if someone turns on a Remote Sensor Booster II, they will see at least the 5% difference between the Sensor Booster I and II, plus any gains seen by the addition of a single sensor booster at the highest diminishing returns.

Almost all modules that boost or penalize a stat affected by stacking penalties will say so in their description: "Penalty: Using more than one type of this module, or similar modules that affect the same..."

Stacking penalties also affect some remote modules such as the Remote Sensor Booster, Sensor Dampener, Tracking Disruptor and the like. These can come from many different sources and can interact with modules fitted on the ship. Stacking penalties are cumulative for all sources, local or remote.

Resistances

Resistances are best thought of as reductions to incoming damage. Each mod affects one or all of the four resistances for each layer of defence. It's easy to see that the −25% EM Damage Resistance Bonus of the Multispectrum Shield Hardener I on a ship with 0% EM resistance would reduce incoming damage by 25%. If the ship has 20% thermal resistance already, then you need to multiply the penalties to incoming damage together:

20% base resistance [math] ( 1 - 0.2 ) = 0.8[/math]

25% Multispectrum Shield Hardener [math] ( 1 - 0.25 ) = 0.75 [/math]

[math] 0.8 \times 0.75 = 0.6 [/math]

[math] ( 1 - 0.6 ) = 0.4 [/math] or [math] 40\% [/math] resistance.

Besides the base resistances of the ship and the Damage Control module, all resistance rigs/modules suffer a stacking penalty. The stacking penalty is ordered highest to lowest per resistance, not per rig/module, which means the highest resistance module for that resistance is calculated first, even though that may not be the highest resist module for another resist.

For example, a ship with base shield resistances, an Multispectrum Shield Hardener I, an Anti-EM Shield Hardener I, a Thermal Shield Hardener I, and a Damage Control I would have the following.

EM: [math] (base)\ 1.0 \times\ (DCU)\ 0.925 \times (EM\ Shield\ Hardener) 0.5 \times (Multispectrum\ Shield\ Hardener\ (diminished))\ (1 - 0.25 \times 0.8691) = 0.361 [/math], or [math] 64\% [/math]

Thermal: [math] (base)\ 0.8 \times (DCU)\ 0.925 \times (Thermal\ Shield\ Hardener\ I)\ 0.5 \times (Multispectrum\ Shield\ Hardener\ (diminished))\ (1 - 0.25 \times 0.8691) = 0.289 [/math], or [math]71\%[/math]

Kinetic: [math] 0.6 \times 0.925 \times 0.75 = 0.416 [/math], or [math]58\%[/math]

Explosive: [math]65\%[/math]

Three Multispectrum Shield Hardeners, due to diminishing returns would provide much lower EM and Thermal (38% and 50%) with only a 63% kinetic resistance.

Alternatively, a slightly less complex calculation is that a resistance module improves resistance but only on the remaining part. Using our Multispectrum Shield Hardener I example above, the ship has a 20% base thermal resist profile already. So, the Adaptive Invulnerability I module applies its 25% but only to the 80% remaining hole (i.e. it provides 25% of 80% => 20% effectiveness) and our thermal resistance is now 40%.

Further reading

• A working example for fitting a ship Fitting A Ship (Working Example)
• A summary reference of the various types of modules and rigs that you can fit on your ship: the Fitting Modules and Rigs Guide.
• When planning your ship fits keep in mind that often modules are stacking penalized. For further reading on stacking check out the Guide on Stacking Penalties.