How do I calculate dragon's Spell Resistance?

[Max Caysey]

Hi...

So I have been searching through Monsters Manual and Draconomicon, but I can't find the bloddy rule. I'm assuming something like ½ HD + Cha modifier, but that does not seem to marry up!

Can anyone help?


Cheers!!!

[tyckspoon]

It's not calculated, as best as I can tell; each age category of dragon just has an assigned spell resistance. It's one of the properties that advances when the dragon gets older and is not directly associated with or derived from any of their other statistics. (Unless they take Awaken Spell Resistance as a feat, in which case it's just set = HD.)

[zlefin]

I agree it appears to largely be ad hoc. it doesn't correspond to HD or account for stat changes.
I scanned through several entries in the srd trying to figure out a best fit formula;

for old and older dragons it seems to very consistently be SR = CR+6
for younger dragons it can go as high as SR = CR+8 the difference never increases as a dragon ages, it just gets smaller sometimes until it hits that 6 difference.
so I'd say they just ad-hoc'ed it using CR as a guide.

[ViperMagnum357]

It depends on the species, excepting things like class features, feats and templates. Once True Dragons get past Great Wyrm, the Advanced Dragon template from the ELH takes over, and the Dragon's Spell Resistance increases by 2 per age category (every 3 RHD past Great Wyrm). I think that is where people are remembering a regular progression.

[Remuko]

a dragon with con 13+ can take "Awaken Spell Resistance" to gain SR = HD or existing SR+2 whichever is higher. Each time after the first it just gives +2 to SR.

[Max Caysey]

Thank you all for your answers... They seem to conform with what I already saw myself...

Would have been nice, if the SR was tied to ½ HD + Cha modifier, like breath weapon DC --- oh well!