Related note - to convert between raw and effective HP, you'll need to know the resistance you're looking at. The formula to use is:
EHP = HP/(1-RST/100)
The method that's generally used to figure out EHP of a ship would be to average the resists of the shield, then the armor, then the hull, and use the formula listed above on each component.
So, it ends up being:
(Total EHP) = (Shield EHP) + (Armor EHP) + (Hull EHP)
(Total EHP) = (Shield HP)/(1-RST/100) + (Armor HP)/(1-RST/100) + (Hull HP)/(1-RST/100)
Where the resists for each component are based on the analytical method you choice, say averaging the resists like stated above, or focusing on one damage type (like, if you know what type you will face).
Hope that clears it up for you
. That being said, EFT calculates it for you automatically, if you have it - if not, get it!