One thing you’ll notice in Diablo 3 very quickly when you start to move up in difficulty as that while you have a certain amount of hit points which are directly effected by Vitality. The actual damage, and effective HP will often be dramatically different from the hit points displayed on your bottom left circle. Now if you’re a high-level Inferno player looking for complete, pinpoint accurate equations I highly recommend you check out this fantastic effective HP calculator over at github. However, we’ve worked at D3SG to develop a very simple version that uses a few, very important metrics to calculate the EHP of your character. This is especially useful when making broad comparisons between items. How does it effect my character if I add armor vs. vitality vs. resists? Is it better to stack one of these metrics and ignore the others? Well the answer depends alot on your specs. Let’s take a closer look.
Effective HP Calculations
In Diablo 3, there are two primary forms of damage mitigation (we talk about dodge in the limitations section), these are Armor and Resists. Your actual HP is effected by Vitality and % Life. For simplicity’s sake we’re not including % Life in our calculator. When acquiring resistances via items, the most effective way is to acquire items with the + All Resistance attribute. The final important factor in the calculation is monster level. You can see monster levels at www.d3db.com, but for Inferno they are 61 for Act 1, 62 for Act 2, 63 for Acts 3 and 4. Alright so here’s the equation for Armor Damage reduction:
Armor Damage Reduction = Armor/(50*Monster_Level + Armor)
Easy enough. Here’s the equation for resistance damage reduction:
Resistance Damage Reduction = Resistance/(5*Monster_Level + Armor)
Very similar. You can clearly see from this that resistances are working on a scale of 10 differently from Armor. Now how do they combine? Very simply it turns out.
Total Damage Reduction = 1-(1-Armor Damage Reduction) * (1-Resistance Damage Reduction)
Now, what’s my HP and eHP?
HP = Vitality * 35
eHP = HP / (1-Total Damage Reduction)
Great! This is essentially all our calculator does. Makes life easy for you.
How do I use this calculator? Well it’s simple. Simply hit I when you’re in a game and then hit the Details tab. You should see your Vitality and Armor upon hitting I, now select the most commonly listed resist value from your resists. Now input these values into our calculator and you will see your EHP.
Our calculator computes in the simplest fashion and as a result should not be used for high-level decisions on buying expensive gear. However, it is a quick, easy method to get quick calculations without having to do a ton of work. It is especially inaccurate for some of the passive skills of the Monk as well as Energy Armor/Force Armor from the Wizard. You’ll also note that we didn’t factor in Dexterity into this. This is because Dexterity effects a dodge rate, which is a bit different. While it definitely helps your survivability, it will not reduce damage from shots that connect. Instead dodge % chance will just give you a chance to avoid damage altogether. This is a really important aspects to Monks survival, so please take that into account when using our EHP Calculator.
NOTE: This calculation also differs slightly for Monks and Barbs because of the additional 30% base resistance that they get. I’ll be building this into the tool shortly.