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Message: <blockquote data-quote="Cadfan" data-source="post: 4111871" data-attributes="member: 40961">Technically, survivability is a function of both HP and AC, and the function is multiplicative, meaning that each improves survivability based on the other.Your survivability is basically [hit points] divided by [[chance of being hit] times [expected damage from being hit]].Lets say that I am hit by a particular enemy on a 13+ (40% of the time), that enemy does an average of 10 damage per hit, and I have 40 hit points.  My survivability is an average of 10 attacks.If I gain 8 hit points, my survivability goes up to 12 attacks.To get the same effect by increasing AC, I would need approximately +1 AC, so I was hit on a 14+.  Rounding is happening here for clarity, strictly speaking I get a survivability of about 11.4.But if I increase my hit points by 8 AND I increase my AC by +1, I get a result that is better than the sum of the individual boosts.  I get a survivability of about 13.7.That may not seem like much, but we're only dealing with +1 ac and 8 hit points.  The effect gets bigger very quickly once you start playing with larger numbers.So... my basic point is just this.  You can't think about hit points without thinking about armor class, and vice versa.   Neither one means much without the other, because what really matters is expected damage per round, and they both factor into that about equally.  A low hit point character with high AC is doomed sooner or later, and a high hit point character with a low AC runs out of hit points very quickly.</blockquote>

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