As luza say, depends on context.
mad, in spanish, can be either 'crazy/insane' or 'angry'
if you're talking about angry, in degrees of ANGRYNESS (haha), from less to more
estoy molesto/a = i'm annoyed
estoy enojado/a = i'm angry / mad
estoy furioso/a = i'm furious (weird to use it in first person)
else... if you're referring to crazyness, there's pretty much just one
estoy loco/a = i'm crazy