Magic Resistance Formula?

[Saber Cherry]

I understand that base penetration is 11, or 7 for an "easily negates" spell. So casting a normal "magic resistance negates" spell with no penetration boost versus a normal MR 10 opponent would put you in the "0+" row with a 54% success rate. 2 additional levels in that spell's path give you a +1 penetration, for 62%, and adding a spell focus gives +2 penetration, for "-3+" 76% success.

The row is determened by the minimum roll difference required. So penetration 11 versus resistance 10 requires a roll difference of 0 or greater, as the penetration has to BEAT, not just tie, the resistance.

-Cherry