Radsplosion Math


Very special thanks to CZ47 for his help with nailing this down. I don’t visit these forums very often, so Discord for questions/comments: Stone_Swan#2717


The heart of the radsplosion calculation is 9x the radiation DOT damage per tick, or 3x the card DOT damage. (Card DOT damage is shown in damage-per-second, while actual dot ticks happen 3 times per second.) This basic formula has been known for a long time, credit to DocStrangelove’s ancient forum post. Note that if you’re using observed radiation DOT values, the DOT damage that goes into this formula ignores elemental multipliers. So if you observe a radiation DOT damage of 400 on an armored enemy, you need to use 800 in this calculation. From there, everything maths out in a manner that should be mostly familiar to those who know damage formulas.

Radsplosions take into account multiple radiation DOTs. But each source of damage can only proc one DOT. For example, a radiation gun with Urad and a 50% radiation ASE procced will still only apply a single radiation DOT, the strongest one. However, Urad or the 50% ASE can add a radiation DOT to your non-radiation grenade, and that extra DOT will combine with the radiation DOT from the gun to increase the radsplosion damage.

Radsplosion Calculation

(For the following multiplications, it is implied that you add 1 to the percentage bonus. For instance, if you have 30% increased elemental damage, its multiplier in the damage formula is 1.3.)

Initial Radsplosion from gun DOT damage:

DOT damage * 9 * gun damage * ASE status effect damage * skill status effect damage * elemental damage * Atom Balm burst damage * splash damage * V1 * global V2 * debuffs

(ASE status effect chance/damage grants +40% status effect damage, despite the card saying 75%)

Initial Radsplosion from non-gun DOT damage:

DOT damage * 9 * skill status effect damage * elemental damage * Atom Balm burst damage * splash damage * V1 * global V2 * debuffs

Add the radsplosion numbers from all sources of radiation DOTs together to get our Total Initial Radsplosion, then calculate bonus elements from this number. We calculate this way because of the differing multipliers between gun vs non-gun sources. For bonus elements, divide out the splash bonus and make a couple other adjustments:

Terror Cryo/Urad/Re-volter:

Total Initial Radsplosion result ÷ splash damage * [0.75 or 1 or 2]

50% ASE bonus elements:

Total Initial Radsplosion result ÷ splash damage * Guardian Rank gun damage * 0.5

For shock bonus elements, keep in mind Tempest’s increased bonus to shock. If Tempest has any skill points, the radsplosion needs to have elemental damage divided out (don’t forget any GR elemental damage) and multiplied back in with the appropriate amount for shock when calculating the shock bonus element. Keep in mind that Tempest adds 2% extra elemental damage to shock per skill point, not 4%, or an extra 10% with 5 points as opposed to an extra 20%.

With our explosion and its bonus elements calculated, combine numbers of the same element and apply the proper elemental multipliers based on your target’s HP bar type.


There is no mayhem scaling with Radsplosions; no true double-dipping, no funny business. If you want mayhem scaling, add Unweave the Rainbow or Fire in the Skag Den or whatever, calculated off of the Initial Radsplosion damage. This means that strong radsplosions are quite simply the result of a strong build. Zane players, note the gun damage portion. Moze players, note the gun damage and bonus element portion. Also, Torgue Cross Promotion + Atom Balm + two passive radius boosts = insane radsplosion radius. Fl4k players, note, um, everything. Amara players, I guess note the bonus element portion, and just do your best.

Radsplosions can irradiate enemies damaged by the explosion. That new DOT is equal to 3/8 or 0.375x the sum of the initial radiation DOTs on the enemy that exploded. Because the source of this new radiation DOT is a radsplosion, training all of your original sources of radiation on these newly-irradiated enemies will add to the radiation DOTs, resulting in a radsplosion stronger than the first one.

Radsplosions have a base radius of 350. For context, a regular nova shield has a radius of around 700, and the Frozen Heart (the widest-radius nova shield) has a base radius of 1500.

The radiation proximity aura does not apply a DOT to nearby enemies - each tick is its own instance of damage. Because of this, however, each tick gets bonus elements, and those bonus elements can proc DOTs while the original aura cannot. A 50% radiation ASE or Urad anointment, therefore, can spread true radiation DOTs around without the need for radsplosions.

Shields like the Red Suit or the Ember’s Blaze with Urad create negligible radsplosions. Though their damaging aura is mayhem-scaled, the actual radiation DOTs that they can proc are between 300 and 400 damage per tick with a level 72 shield before applying any bonuses. Even with lots of bonuses, a base radiation DOT that low will have practically no impact on Mayhem 10/11, outside of possible Harmageddon benefits.

A radiation Hex, commonly used to add radsplosions to the field, can proc one of two radiation DOTs. A weaker one, procced by the beams, that has a base radiation DOT between 500 and 600 damage for a level 72 mayhem 10 Hex - negligible. The much more respectable card DOT damage is procced when the grenade itself impacts an enemy, either when it’s flying around and makes contact or when it explodes out of existence at the end of its life. With light field testing, it seemed about 50/50 which DOT got procced, if one procced at all.

Things that don’t increase or add to radsplosion damage: ASE 75/40 status effect chance/damage on non-gun sources, 40% Siren radiation ASE anointment, grenade damage boosts, Forceful Expression, On Grenade Thrown anoint, critical hits

Fine Print for Calculating Radiation DOTs

For cryo guns that proc a radiation DOT through Urad or Next Two Mags radiation or a 50% radiation ASE, you can find your gun’s card DOT damage by multiplying its card damage by the cryo efficiency. For example, a cryo gun that lists 10,000 card damage with a cryo efficiency of 150% has, effectively, 15,000 card DOT damage, and a 50% radiation ASE used in conjunction with this gun would deal 7,500 radiation damage per second (or 2,500 per tick).

For kinetic guns, you would have to compare it to an elemental version, and apply the same DOT damage (or cryo efficiency) to card damage ratio that you see on the elemental version to the kinetic version’s card damage.

For kinetic grenades, the same applies, however on all grenades a 50% ASE calculates as 100% as far as the DOT it procs is concerned. For example, you have a 10,000 damage kinetic grenade with 50% radiation ASE. To find out the DOT damage that the ASE would apply, you have to compare it to an elemental version of the grenade. Let’s say a corrosive version of the grenade has 8,000 card damage and 6,000 card DOT damage. Taking that same 4:3 ratio to the kinetic version we calculate that it has a hidden card DOT damage of 7,500. And since the 50% ASE calculates as 100% for grenade DOTs, the ASE would apply a radiation DOT that does 7,500 damage per second (or 2,500 per tick).

Cryo grenades, unlike cryo guns, have their cryo efficiency disconnected from the card/DOT damage of all other elements (including kinetic) of the same grenade. Taking the above example, while we might think a cryo version of that grenade has 75% efficiency, it will more than likely be significantly higher, like 100%. Therefore, a cryo version of the above grenade, with 8,500 card damage and 100% efficiency will have its 50% radiation ASE (calculated as 100% for the DOT it applies) proc a DOT of 8,500 damage per second (or 2,833 per tick), an amount greater than the kinetic version of the grenade.

Precise Atom Balm Calculation

The Aura Burst Damage and Aura Burst Radius percentages are calculated based on item level and rounded on the card. For a more precise number, use the following formula:

0.1 + (0.00333 * (Level - 27))

Atom Balm Stacking

If you unequip and re-equip the same Atom Balm artifact, the Aura Damage bonus (and the Aura Damage bonus only) stacks, and it keeps stacking every time you do so. Even if you drop the artifact and pick it up again, the game remembers how many times it has been equipped and keeps the appropriate amount of stacks for the Aura Damage. Each individual Atom Balm has its own stack counter. The stacks persist through fast travel and death. They are only lost upon save/quit.


Fairly niche bit of info, but considering the synergy of Cryo/Radiation this is actually really helpful for proper min/maxing.

Nice write up @Stone_Swan ! ! !


One of the final frontiers of BL3 math has been conquered. Now we just need to pester someone to finish sticky math, cuz I ain’t touching that ■■■■ with a 10 ft pole.

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Much of that went over my head unfortunately but am i reading right in that to get max radsplosion damage, using a cryo gun with n2m radiation or urad is the way forward?

Thank you @Stone_Swan! Much respect.

@kitehighland I’m kinda like you, my eyes glaze over when I see this much math in the game, but the general gist I got was that lots of things affect your radsplosion damage, including the overall gun damage. Because the overall gun damage will typically (almost always?) be higher on a cryo version of a weapon that also can come in other elements, yeah, you wanna use cryo for max extra element rad damage.

This is one of the reasons I like to run cryo on my Urad builds wherever possible - the base damage on these weapons is higher, parts being equal on the two weapons. And you also have cryo and rad to deal with all resistances (plus any other ASE elements also).

Hopefully I understood your question, apologies if not LOL

Absolutely spot on bud, much appreciated.

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I just made a fairly significant adjustment to the formula(s). Skill status effect damage boosts, like Anima, do in fact increase radsplosion damage. And they’re multiplicative with the ASE status effect chance/damage anoint.

Why didn’t I catch this before? Well, I was testing with Amara and my action skill element was set to cryo, so that when I Phaseslammed to proc Laid Bare, I wouldn’t DOT the enemies. For those that don’t know, having cryo as your action skill element completely breaks Anima, making it not function at all. It was apparently something I forgot, and it confused me for a while because I thought I saw Anima adding to the radsplosion a few days earlier. I re-tested today with a different action skill element and Anima’s boost was factored into the formula. Just be aware, Amara players, that it won’t help you at all if you’re using cryo as your attuned element.

Sorry for the mishap.


We will let your error slip . . . This time

It will take far more than one oversight to warrant much criticism on a formula this finicky to decode.

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I don’t use urad almost ever, but may add some to my cryo-focused, Dahl-allegiance Zane. Bloodsplosion chains were one of my favorite things to do with Krieg.

Next 2 mags radiation is good, urad isnt actually needed.

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So to make sure I understand this right, here’s how I plan on working this (without working what appears to be a bug with Atom Balm, though if that’s what it takes to throw some Krieg-worthy rad-splosions, I won’t say no).

  • I’ve got a nice cryo Mngwa that I’ll be taking to Earl to roll for an anointment to get the next two mags to throw 100% bonus radiation damage. Zane will be wielding this with MNTIS, so it’ll be easy to trigger this anointment. The URad anointment seems like it would hit harder, but I’ll see if this hits as I like this way first.

  • I’ve got a radiation Old God that I’ll give to him from one of my FL4Ks that should bump the radiation damage for both the DoT that goes into the radsplosion as well as the radsplosion itself? I don’t actually know if/where it hits that equation (is it V1 or V2 type, or something else?). It currently has a corrosive anointment… should I bother Earl for a different one? I was considering a “status effect chance with Barrier” anointment, but Zane here has Our Man Flynt, so getting DoTs to proc shouldn’t be an issue (though he is also using Barrier if needed).

  • He’s got a decent purple Atom Balm with 28% radiation damage, but one of my other characters has one with 55% AoE damage, which I think applies here? Should I swap? The other modifiers are random things like reload speed or whatever.

  • What’s the best COM to add to the radsplosions (not the best because it’s some meta… I regularly use Techspert and Ringleader COMs, so have no qualms about sacrificing my total damage output if it’ll feed the radsplosion output). I have a Cold Warrior… maybe I get lucky with radiation coming up as one of the random elements? I will be freezing enemies constantly.

  • I can’t throw grenades reliably with this build, so unless you think swapping out the radiation Old God with a Revengenader (which will allow me to throw grenades at will), what kind of grenade (and anointment) is best here? It’s Piss is probably the best technically, but I might like a singularity to try to keep enemies within range of everyone’s radsplosions. As a separate radiation source, maybe an actual radiation grenade? If the Old God is better, I can equip any grenade just to have the anointment on deck. Any old grenade with 50% rad damage for ten seconds on action skill end? Does this count as “separate” from “next two mags” anointment when calculating damage, or are those anointments similar enough that one is skipped/wasted?

Thanks in advance! I love this game mechanic, and am glad it’s available to all characters. :metal:

Can’t state the “best” com, but as none of them can roll with an elemental damage - splash damage would be better

Elemental damage % is seperate in the equations, so would be multiplicative with v1/v2 and other sources

I would recommend the atom balm with aoe if your using the old god, rad % with any other solong as splash is on com

And 50% shield and grenade anointments are seperate - they apply to radsplosions aswell

I agree, as urad will apply to both your weapon damage aswell as the radsplosions, 100% N2M only applies to the base weapon (does add into radsplosion still but not to the same degree)