Quote:

**Sanji Watsuki**:

(100/130) - (100/((100) + (30-12)*0.85)) should model the % of damage you could expect to do more against a base level magic resistance. Basically, a 9.8% difference. By comparison, if they buy a 50 MR item, the difference changes to (100/180) - (100/((100) + (80-12)*0.85)) or 7.8%. Either way, it is a solid damage increase overall. For reference, this means 1000 burst magic damage results in 78 more damage.

It's (100/130) - (100/((100)+(30*0.85-12)). The % applies before spell pen (but after -magic resist).

1:1 ratio

300 * (100/130) = 230 base damage

351 * (100/(100 + (30*0.85))) = 279 damage

300 * (100/((100) + (30*0.85-12))) = 264 damage (+4 from your calc)

750 * (100/130) = 577 base damage

801* (100/(100 + (30*0.85))) = 638 damage

750* (100/((100) + (30*0.85-12))) = 661 damage (+11 from your calc)