I know when evaluating gear one of the standard equations is

1 ac = 5 hp

Can I get opinions on the follow equations

1 shielding = ??? hp

1 shielding = ??? ac

1 avoidance = ??? hp

1 avoidance = ??? ac

??? shielding = ??? avoidance

I know I am not including Spell or Dot shielding but this is a tank question.