Stats Guide - Effective HP

The "Effective HP" (or "EHP") are a bit special. They cannot be considered as a legacy stat,
but rather as hidden result after increasing resistance-related stats

These don't constitute a separated stat since they are determined through your current max. HP and damage reduction rates. These can be considered as "the real HP you have while facing an enemy": basically, an enemy will deal you reduced damage if you have armor, damage reduction etc. but you can also say you have more HP against him, considering he was dealing non reduced damage. The Effective HP increase with an exponential behavior as your damage reduction value increases!

The formula to calculate Effective HP out of the defense rate here is:

EHP = Max. HP / (1 - defense_rate)

An example to illustrate:

• You have 15,000 HP and 30% defense rate. Using the formula above, you obtain ~21,429 EHP (15,000 / (1 - 0.3)).
• Now if you still have 15,000 HP but 40% defense rate, you have then 25,000 EHP => ~14% more EHP than with 30% def. rate (15,000 / (1 - 0.4)).
• And now, if you still have 15,000 HP but 50% defense rate this time, you have then 30,000 EHP => ~16.7% more EHP than with 40% def. rate even though the gain is still of 10%!

To go further, the gain would be about 50% EHP between 90% (150,000 EHP) and 95% (300,000 EHP) of defense rate, and about 60% between 97.5% (600,000 EHP) and 99% (1,500,000 EHP) of defense rate. I guess you got the involved logic here.

Except for PvP content or fun purpose, aiming for the maximum EHP has no proper use for endgame PvE content since bosses use to hit with pattern attacks ignoring resistance and scaling on your Max. HP. The EHP are only efficient to enemies dealing random damage taking your resistance into account, such as classic mazes or PvP content.