# Thread: Effective Health equations frying my brain

1. King of Noobs
Join Date
Dec 2007
Posts
21

## Effective Health equations frying my brain

I have yet to see a formula for effective health (or one for mitigation for that matter) that makes the least bit of sense to me. I've looked at Satrina and Cider Helm's guides and just wound up scratching my head a lot.

2. Well the basic thing to know is the amount of damage a boss does to you is not the same amount that he tries to do to you.

Example: A boss tries to hit a warrior in battle stance for 10k damage, but the warrior has enough armor to reduce incoming attacks by 40%, so the boss only does 10k*0.6 = 6k.

Example 2: A boss tries to hit a warrior in defensive stance for 10k but the warrior has enough armor to reduce incoming attacks by 60% and def. stance reduces damage by 10%, so the boss only does: 10k*0.4*0.9 = 3600 damage.

In both examples, the boss tries to do 10k, but because of AC and your stance reduction, he ends up doing much less (the amount you see on your screen).

Effective health is kinda like reversing this thought process. You take the amount of damage you are interested in, divide by your reductions (inverse of multiply) and that tells you how much damage the boss tried to do. Since EH really worries about tank death, you use your HP pool as the amount of damage a boss does:

HP /(Armor_Reduction*Stance_Reduction) = EH

Note when I say Armor_Reduction, if you reduce damage by 60%, the Armor_Reduction value would be 40% (I know, it is a bit backwards, but I don't really know the correct term to name it).

So if you have 20000 HP, your armor reduces damage by 60%, and are in defensive stance, then your effective health is:

20000/(0.4*0.9) = 55556 Effective Health.

I.E. The boss must try to do 55556 damage to kill you, which is then reduced by armor and stance down to 20000.
Last edited by jere; 01-14-2008 at 09:34 AM.

3. King of Noobs
Join Date
Dec 2007
Posts
21
I'm pretty sure I understand how Effective Health works, it's just figuring out how much I have and how much I can have that I'm having trouble with.
Originally Posted by jere
HP /(Armor_Reduction*Stance_Reduction) = EH

Note when I say Armor_Reduction, if you reduce damage by 60%, the Armor_Reduction value would be 40% (I know, it is a bit backwards, but I don't really know the correct term to name it).

So if you have 20000 HP, your armor reduces damage by 60%, and are in defensive stance, then your effective health is:

20000/(0.4*0.9) = 55556 Effective Health.

I.E. The boss must try to do 55556 damage to kill you, which is then reduced by armor and stance down to 20000.
So basically I divide my HP by my armor reduction multiplied by my stance reduction?

I have 12688 health and 13053 armor.

According to Blizzard's tooltips that means I have 55.28% damage reduction from armor and 10% damage reduction from Defensive Stance. I must have misinterperated the equation because I only wound up with 2295.22 Effective Health.

4. Originally Posted by Razor
I'm pretty sure I understand how Effective Health works, it's just figuring out how much I have and how much I can have that I'm having trouble with.
So basically I divide my HP by my armor reduction multiplied by my stance reduction?

I have 12688 health and 13053 armor.

According to Blizzard's tooltips that means I have 55.28&#37; damage reduction from armor and 10% damage reduction from Defensive Stance. I must have misinterperated the equation because I only wound up with 2295.22 Effective Health.
13053 AC gives 52.18% reduction
Def. Stance gives 10%

12688/(0.4782*0.9) = 12688/(0.43048) = 29480.9

Notice that I use 1 - .5218 = .4782 and I use 1 - .1 = .9

EDIT: oh and while blizzard's tooltip says you have 55.28% reduction from armor, that is against a level 70 enemy. Against a boss,you would have 52.18% reduction, which the tooltip doesn't show.

5. King of Noobs
Join Date
Dec 2007
Posts
21
Originally Posted by jere
13053 AC gives 52.18% reduction
Def. Stance gives 10%

12688/(0.4782*0.9) = 12688/(0.43048) = 29480.9

Notice that I use 1 - .5218 = .4782 and I use 1 - .1 = .9

EDIT: oh and while blizzard's tooltip says you have 55.28% reduction from armor, that is against a level 70 enemy. Against a boss,you would have 52.18% reduction, which the tooltip doesn't show.
So I divide my damage reduction from armor by 100 and repeat the step for my reduction from the stance I'm in (in order to convert the percentages to decimals).

Then I subtract both my damage reduction from armor and my damage reduction from stance from 1.

Then I divide my health by these numbers multiplied together? That's what I wanted to know.

Also, knowing that the tooltip only shows my mitigation against a lv 70 target, how do I figure out my mitigation against a lv 73 (boss)?
Last edited by Razor; 01-14-2008 at 10:37 PM.

6. Established Registrant
Join Date
Sep 2007
Posts
317
The damage that you take from a boss is the damage *after* mitigation by your armor. Effective Health is the damage that you are able to take *before* mitigation. This is important because comparison of Effective Health is the easiest way to compare Time-To-Live between two tanking setups. There are of course other ways, but Effective Health uses a common denominator (Effective Health and Raw Damage) to expedite this comparison.

Using the HP/armor model of Effective Health (ignoring block), the following scenario just barely results in death:

Post Mitigation Damage = HP

Post Mitigation Damage is calculated by:

Post Mitigation Damage = Raw Damage X (1-Mitigation Percentage)

Substituting in HP for Post Mitigation Damage and playing around with the equation gives:

Raw Damage = HP / (1-Mitigation Percentage)

This is the amount of Raw Damage (ie. before mitigation) that will kill you, also your Effective Health considering only HP and armor. Warriors also have a multiplicative 10&#37; damage mitigation from Defensive Stance and Paladins have 6%, therefore:

Post Mitigation Damage = Raw Damage X (1-Mitigation Percentage) X (1-0.1)

Raw Damage = HP / ((1-Mitigation Percentage)X0.9)------> Warrior
Raw Damage = HP / ((1-Mitigation Percentage)X0.94)-----> Paladin
Raw Damage = HP / (1-Mitigation Percentage)------------> Druid
Last edited by Finelle; 01-15-2008 at 01:56 AM.

7. Established Registrant
Join Date
Jul 2007
Posts
276
you don't need to know all the maths.

Gear up for Stamina and Armor, maintain critical strike immunity and GG.

8. > Kaze
Join Date
Aug 2007
Location
Virginia
Posts
528
Tankpoints has an eh calc built in, and there is one on this site's main page as well.

9. Originally Posted by Razor
So I divide my damage reduction from armor by 100 and repeat the step for my reduction from the stance I'm in (in order to convert the percentages to decimals).

Then I subtract both my damage reduction from armor and my damage reduction from stance from 1.

Then I divide my health by these numbers multiplied together? That's what I wanted to know.

Yep, exactly!

Just for clarity, the EH equation is:

Hit_Points/((1-DR_armor)*(1-DR_stance))

Just take a look at the values I used in my earlier example and try to see how I got them. Oh and definitely use decimals. You almost never use percentages as is in math, they are typically handled as decimals (0.5218 for 52.18&#37; )

Originally Posted by Razor
Also, knowing that the tooltip only shows my mitigation against a lv 70 target, how do I figure out my mitigation against a lv 73 (boss)?
To Figure out how much DR_armor you have against a 73, you use:

DR_armor = AC/(AC+11960)

Of course, DR_stance = 0.10 for warriors (0.06 for paladins)

10. Established Registrant
Join Date
Aug 2007
Location
Notlob its a palindrome
Posts
736
grr at the difference between RF and def stance:
15k health 60&#37; reduction
Warrior=41666 EH
Diff = 1773
16k health and 64% reduction
Warrior= 49382.7
Diff= 2101.4 EH

As gear level goes up EH gap goes up -.^ and people told me 4% was not a big deal how wrong they are. How wrong they are. Unless i did my math wrong..

11. Established Registrant
Join Date
Sep 2007
Posts
317
Hmm? I haven't done full calcs, but the higher stamina scaling for paladins should cancel the 4% difference out. Since the 4% is pre mitigation as your equations point out, it doesn't scale more than linearly. Raid buffed, it's trivial to surpass the stamina threshold at which paladin health exceeds warrior health at the same gear level.

12. King of Noobs
Join Date
Dec 2007
Posts
21
Originally Posted by jere
To Figure out how much DR_armor you have against a 73, you use:

DR_armor = AC/(AC+11960)

Of course, DR_stance = 0.10 for warriors (0.06 for paladins)
Armor divided by armor plus 11960 right? So if I had 13,000 armor I'd have 52.08% mitigation against a lv 73?

13. Originally Posted by Razor
Armor divided by armor plus 11960 right? So if I had 13,000 armor I'd have 52.08% mitigation against a lv 73?
Yep.

If you are interested in mobs less than 73, then you need to change that 11960 number. There is a formula for it on wowwiki to calculate what number needs to be there based on level.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts