I'm attempting to analyze the armor of Fallout 4 to have some baseline to determine the "best" set or mix of sets of modular, non-powered, non-legendary, non-specific armor, but I need to know how incoming damage is calculated for the PC.

The formula I am currently using is as follows:

finalDamage = paperDamage*((paperDamage*0.15)/DR)^0.365

Where finalDamage is the amount subtracted from your HP bar, paperDamage is the incoming damage "on paper", and DR is the total DR from all armor pieces, headwear, eyewear (Operator's Goggles from NukaWorld), and armored clothing.

To clarify the extent of the question: some amount of damage of some type or combination of types is dealt to the PC. Based on the type or combination of types of the damage and the various resistances possessed by the PC, what formula(s) is/are used to determine the number of Hit Points subtracted from the PC's health bar?

I am not looking for a comprehensive breakdown of all possible damage types or combinations, that's what I want to do. I'm just looking for the formula(s) I need before I plug in numbers and get the final HP loss.

  • How do you plan account for different damage types (ballistic, radiation, etc.), perks, and so forth in your equation? ( Also this is the set of calculators I've always used. ) Sep 30, 2019 at 5:46
  • Depends on the damage type and perk and how they are factored into the equation. The answer to the question should include differences between equations if they exist. I also need the exact equations so that I can put them into a program, and what the variables mean so that I can modify them as necessary to account for more things. Sep 30, 2019 at 6:25
  • Aren't the equations on the site that Roddy linked an answer to your question?
    – Joachim
    Sep 30, 2019 at 7:42
  • @Joachim In some ways they can be considered an answer. However, I'm no stranger to these wikis, and the standards I am familiar with are that to be considered an "answer", it can't be just a link to another site with instructions to "just look here and figure it out". Including links is often helpful for citing sources or offering additional information beyond the scope of the question, but it is not a substitute. Oct 1, 2019 at 1:57
  • Oh no, that's certainly not what I meant. I'm very much against those myself. I intended it to be an incentive for Roddy to post it as an answer, but wasn't completely sure if the equations posted there where what you're after.
    – Joachim
    Oct 1, 2019 at 10:09

1 Answer 1


You can refer to Fallout's wikia article on damage resistance to understand how damage is calculated in Fallout 4.

The damage coeffecient looks like this

enter image description here

but the ultimate damage is determined as:

enter image description here

But there are a lot of types of damage such as explosive, poison, energy and radiation. It is essential to check the linked wikia article for a comprehensive explanation of how all types of damage are calculated.

As for your question of how the game handles weapons that fire multiple types of damage, this too is answered in the wikia article:

"When something has multiple resistible damage types ... one "hit" resolves as a hit for each damage type applied. Likewise, when something deals both direct and area of effect damage, a target is hit by each one individually. For example... a fully charged shot from the weapon will inflict 6 distinct "hits": energy damage, explosive energy damage, explosive projectile damage, radiation damage, explosive radiation damage and radiation poisoning."

In regards to additional questions in the comments: Incoming damage of two types from one attack qualifies as two distinct calculations- one for each damage type. Energy and explosive are distinct, but there are weapons that can deal two or more types of damage in the same shot such as the Radium Rifle (27 damage ballistic, 50 damage radiation). Again, this is still calculated as two distinct attacks: one calculation for the ballistic damage and a second for the radiation damage.

Regardless, the calculation for each damage type is identical, explosive damage uses the same formula as ballistic damage uses the same formula as energy, etc. The damage type determine what perks take effect and what your armor blocks against. Some damage types, such as poison, have additional effects that only apply after the damage calculation is performed.

As for radiation specifically: Each point of radiation damage you receive removes .1% of your overall health. If you receive ten points of damage from a Gamma Gun your health will be reduced by ten points and your maximum health cap will be reduced by 1%.

  • That is the same formula the OP already posted, and he is explicitly asking how damage types are calculated as part of that formula. I think the link Roddy posted in the comments has all the info the OP needs.
    – Joachim
    Sep 30, 2019 at 18:22
  • 1
    You're right. I misinterpreted the question. I've updated the answer to include combinations of damage types
    – PausePause
    Sep 30, 2019 at 19:27
  • You have found one of the things that is unclear to me. I know of ballistic, energy, and radiation damage reduction. How is "explosive energy" handled? According to the wiki, that's one hit. Is it explosive, or is it energy, or is the "one" hit actually "two"? What about radiation poisoning vs. radiation damage vs. explosive radiation damage? These are not obvious. Oct 1, 2019 at 2:01
  • Also on the wiki are two notes: projectile and close combat weapons use different variables than energy weapons. What's the mathematical difference between these two types, and how does this change the formula? Oct 1, 2019 at 2:04
  • All of these questions are answered in the wikia article: Incoming damage of two types from one attack qualifies as two distinct calculations- one for each damage type. Energy and explosive are distinct, but there weapons that can deal two types of damage simultaneously. As for radiation specifically: Each point of radiation damage you receive removes .1% of your overall health.
    – PausePause
    Oct 1, 2019 at 16:27

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