Combat Maneuver Defense
Each character and creature has a Combat Maneuver Defense (or CMD) that represents its ability to resist combat maneuvers.
A creature’s CMD is determined using the following formula:
CMD = 10 + Base attack bonus + Strength modifier + Dexterity modifier + special size modifier + miscellaneous modifier
Special Size Modifier
The special size modifier for a creature’s Combat Maneuver Defense is as follows: Fine –32, Diminutive –16, Tiny –8, Small –4, Medium +0, Large +4, Huge +8, Gargantuan +16, Colossal +32.
Some feats and abilities grant a bonus to your CMD when resisting specific maneuvers.
A creature can also add any circumstance, deflection, dodge, insight, morale, profane, and sacred bonuses to AC to its CMD.
Any penalties to a creature’s AC also apply to its CMD. A flat-footed creature does not add its Dexterity bonus to its CMD.
If your attack roll equals or exceeds the CMD of the target, your maneuver is a success and has the listed effect.
Some maneuvers, such as bull rush, have varying levels of success depending on how much your attack roll exceeds the target’s CMD. Rolling a natural 20 while attempting a combat maneuver is always a success (except when attempting to escape from bonds), while rolling a natural 1 is always a failure.