In this guide we will go over the some of the things one must consider when making a build and determining how many shots you can survive.

## Damage Reduction

Damage reduction tells how big of a % is subtracted from what the game considers 100% damage, or in other terms by what percentage is the damage reduced. For example we shall consider Frenzy Aced, which gives total of 25% damage reduction. Note here that the game doesn’t consider the 10% from basic, which is implied by the description: “Damage taken is now reduced by 25%”.

Anyway, the 25% damage reduction means that the units will do 75% of the damage they would normally do. So the damage is scaled

Damage dealt = Unit damage*(1-Damage Reduction)

Here unit damage is what the unit will deal without damage reductions. For example Death Sentence Heavy SWAT is 225.

**How does damage reduction stack?**

Logical question which follow after we think about how damage reduction is calculated is; how does damage reduction stack? Answer to this is that, it is multiplicative:

Consider damage reduction of 25% combined with 10%, this gives us total damage reduction:

Total damage reduction = 1-(1-0.25)(1-0.10) = 0.325, or around 33%

Note here that (1-0.25)(1-0.10) is equal to the factor by which the damage is reduced(let us call that damage multiplier), which is 1-damage reduction. Thus we get 1-damage multiplier = damage reduction so:

Damage dealt = Unit damage*(1-total damage reduction)=Unit damagetotal damage multiplier

**If we want to be fancy we can write all these in terms of actual maffs, which is bit cleaner**

As an example let us consider when we have Frenzy Aced(25%), Quick Fix Aced(10%) and we get Combat Medic basic(30%) buff while reviving on death sentence difficulty.

Here we would have number of damage reductions n=3, unit damage for heavy 225 and damage reductions r_1=25%,r_2=10%,r_3=30%, thus the damage by a single heavy shot to you would be

D=225*(1-0.25)(1-0.10)(1-0.30)=106(rounded)

## Damage Absorption

Damage absorption is very simple, it is the amount by which the damage is reduced, applied last. Such that damage reduction is applied first. Damage reduction is additive as far as I know, meaning that for example 4 damage reduction and 20 damage reduction combined is just 24 damage reduction.

Thus we get that:

Damage dealt = Unit damage*(1-Total damage reduction)-Damage absorption.

So damage absorption from forced friendship aced which is max 4 damage would reduce the previous cases damage to 106-4=102

## Armor Gating & Breakpoints

Quick note on armor gating which is an important for many builds such as anarchist for which armor gating is main mechanism to avoid damage.

Armor gating happens when the damage you’re about to receive is greater than the amount of armor you currently have. Payday 2 works in a way when you are shot you cannot take hp damage when you take armor damage, meaning even if you had 1 armor left a 225 shot will only do 1 damage to you, breaking your armor.

Note that snipers are an exception to this.

**Armor breakpoints**

Because of armor gating we have armor breakpoints, since if your armor value doesn’t exceed the damage value, all the extra armor is basically useless. (Overly simplified as there are many sources of damage)

When considering how much armor you need, consider how many shots it can take before breaking. For example heavy swat on death sentence dealing 225 damage means that as far as heavy damage is concerned Suit and ICTV at 221 are equal.

But there are other things to consider, such as how many shots you can take from other units and the grace period, which complicates the discussion in this aspect.

**Grace period**

Grace period is an interval of 0.45s/0.35s(Mayhem+) during which you cannot take damage from sources that deal less damage than the source you just took damage from.

This means a light shot (68 dmg) followed by a heavy shot (225) will ignore the grace period and if, for example, you run anarchist zerk with suit you will be downed instantly (unless you have the god mode from anarchist ready).

So, it can be beneficial to have enough armor to tank a light shot without breaking the armor if you want to avoid grace shots and in general. Though very few builds actually have this as consideration as usually it’s either ICTV or suit. LBV can benefit from it but it requires iron man basic with die hard aced.

**In my opinion in summary**

Often the most important consideration is how many heavy shots you can take, both to your hp and armor.

To do this you can calculate the actual damage dealt when you have damage reductions for example as we discussed above. For example if you run frenzy basic with ictv (221 armor), you can survive two heavy hits.

This is important because with some builds you might not need ICTV to survive two heavy shots for example frenzy crook.

## Health and Armor

Health and armor calculations in payday 2 are additive, such that the total health is just sum of all the health multipliers.

For example 30% and 10% health increase counts to be a 40% increase in health. Which is calculated from the base health of 230 such that 230*1.4=322

Same goes for armor.

**Things like anarchist in with bot boosts might be harder to calculate:**

Anarchist converts 50% of your hp into 120% of armor, meaning total armor is base armor+115*1.2

So for suit 20+115.1.2=158.

Iron man basic would multiply that by 1.3.

Partners in crime aced would increase your hp by 1.3 which in turn would increase your armor, but the answer as to how much isn’t trivial. The partners in crime still increases your hp as if it wasn’t cut in half, thus the actual increase to armor by partners in crime is much greater than the 115*1.2*1.3 as one could expect. Instead you get about 240 armor with a convert, meaning the calculation is

Total armor = 20+(115+230*0.3)*1.2=240

And the bot boosts of 60 hp and 30 armor would give us

Total armor =20+((230+60)/2+(230+60)*0.3)*1.2+30=328(rounded)

So the boost is considered as boost to base hp, which is insane.

Adding iron man basic to this gives us

Total armor =(20+((230+60)/2+(230+60)*0.3)*1.2+30)*1.3=328*1.3=426(rounded)

(Note: Crew chief would add to the multiplier 0.3 (535))

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