What does sacrificing do? If it erases the body mass which holds consciousness then sacrificing a human (body) should not remove all living organisms and other parasites like bacteria or lice.

If sacrificing means erasure of consciousness (about the same as death) then we should also assume there is no loss of mass. If consciousness is the determining factor of how strong a magic is, how should we quantify it? The number of consciousness from different bodies? The intelligence of the consciousness? The summation of the consciousness as a whole?

If we're talking about the number of consciousness, would this be consciousness that only the caster is aware of? Or all consciousness in a specific magic circle? For ease of argument say both is true.

That would allow a caster, who is only connscious of consciousness within a specific area to know how much and what would be sacrificed. Taking all lives being equal, we can take the number of consciousness to be sacrificed the determining factor of a magic's strength.