# Is Resist Magic multiplicative or additive?

I know this has been asked as a general question before and the consensus here is that each item that adds a resist magic percentage is multiplicative but UESP reckons it is additive with an 85% hard cap. With 1.3 out now have we any more confirmation which is correct?

• What? It's additive like every other resist / fortify / etc. thing. Where is it said it's multiplicative? – agf Dec 16 '11 at 14:19
• @agf if you find a source or show that you've tested this, feel free to write an answer – l I Dec 16 '11 at 14:33

Resist magic sources are additive, but are multiplicative with element resists. I have copied text below I wrote in another post:

Magic resist does reduce elemental damage, but separately from the resists.

( Damage | Absorbed ) = 0 * damage

( Damage | ¬Absorbed ) = (( 1 - magic resist ) * ( 1 - elemental resist )) * damage


Elemental Resists and Magic Resists cap at 85%. Magick absorption caps at 80% (without the breton daily power). Probability( Absorbed ) is just your magic absorption. Each effect is additive with itself up to the cap, then multiplicative with the other effects.

Thus

Expected damage = ( 1 - magic absorption ) * ( 1 - magic resist ) * ( 1 - elemental resist ) * damage


Min expected damage is therefore 0.2*0.15*0.15*damage = 0.45% of original

N.b. we can see, therefore, that it is better to stack a single source of resistance up till the cap than spread it evenly with the possible exception of absorption which will put you in the random hand of fate: Assuming equal chance of element types. However, this is not the case as fire and frost are much more common than shock. So it may be better to have single element fire and frost resistance, than a lower magnitude resist all.

Sources:

EDIT: apologies for formatting. I am new to stack exchange and haven't worked out a clean post style yet.

• If that's not what you were after let me know. (Add a comment below this one with @CRoss). – C. Ross Dec 16 '11 at 15:42
• nice first post, welcome to the site – l I Dec 16 '11 at 17:47
• Whoever 'Community' is (/jk) and whatever you changed, then thanks :-). Reading back on this, I would have phrased/formatted it differently now I am no longer a S/O newb, and if you corrected maths issues then double thanks! – Asdafgh Feb 27 '14 at 0:13