Resistance, the flip side

I touched on making your spell hit more dangerous last time. The flipside this time – How do you reduce the danger from other spellcasters? Obviously, Resistance. But, how much, and how useful?

First let’s grasp the core of spell resistance. If the other side casts a spell that has an effect – fear, blackout, invisibility, or anything like that where it either works or it doesn’t – then resistance increases the chance it doesn’t. If the other side casts a damage spell, then it reduces how much damage comes through. If both are possibilities (slows and causes XXX damage over the duration aka Mind Flay), then both effects of resistances are possible. I’m not going into the single roll theory and its application in this post.

According to posts the Guys at Blizzard have made, the best possible resistance is 75%. And through other posts and some serious study, we know how to get that 75%. Easy, actually — have five times as much resistance as the opposing spell-caster’s level. In fact the formula is fairly simple:

([Resistance value]/[spellcaster level * 5]) * 0.75 = Resist Percent.

Let’s take a lower level to show this. 20-29 BG. You’re facing a 29 spellcaster, and you want to know how useful (or not) the +4 shadow resist ring is going to be.

(4 / (29*5) )* 0.75 = 2%.

Of course we can flip that. ([Resist Percent]/0.75) * ([spellcaster level] * 5) = Resist Rating. So, how much resist do we need to get a 1% change against level 70 spellcasters?

(.01/0.75) *350 = 4.6667

Every 4 and 2/3 resistance gives us 1% chance of the level 70 spellcaster’s spell not working (if all or nothing), and/or reduces the damage by 1%. Wheee.

Prayer of shadow protection II – your “Big one” – is 70 resistance. Against a level 70 spellcaster, that’s approximately 15%.

The math works the same for all the resistances. Bottom line – resistance helps, but it’s not everything.

~ by Kirk on July 24, 2007.

2 Responses to “Resistance, the flip side”

  1. Great post. Especially love the formula given:

    ([Resistance value]/[spellcaster level * 5]) * 0.75 = Resist Percent

    I am having difficulty finding a reliable formula for resistances based on comparative levels.

    For example:

    A level 60 casting on a level 70. (lets assume resistances and spell penetration are zero)

    Is there a formula for this situation?
    If there is, is there one that also ties in related resistances


  2. First note that very few formulas are from the mouths of blizzard – not as one piece. They’re pieced together from partials from Blizzard plus trial and error from players plus (inevitably) a bit of guesswork. So…

    I have the most confidence in the numbers at two places. Those are the official forums of Warcraft (both US and EU, though in my experience the EU crafters tend to put a little more focus on the numbers), and Allakhazam (

    Now as to the other part of your question… I’ve confused you. This almost deserves a long post, but let me do it in short.

    As near as various folk have been able to tell, all attacks are two tables. One determines whether you’re hit, and the other is the actual damage. Pretty consistently, level modifies hit, not damage.

    For spells, resistance (and penetration) are damage modifiers. So if your level 60 hits your level 70, what the lack of resistance and penetration mean is that there’ll be no reduction in damage. (btw – penetration is best considered counter-penetration. If there’s no resistance, there’s no penetration needed.)

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