Is the narrator in the Tell-tale Heart a calculated murderer or mentally insane.

I'd go with the latter, mentally insane. The narrator is an unreliable narrator meaning that we cannot take anything he says as being reasonable. Though he repeatedly states that he is sane, the reader suspects otherwise from his bizarre reasoning, behavior, and speech. He speaks with trepidation from the famous first line of the story: "True — nervous— very, very dreadfully nervous I had been and am; but why will you say that I am mad?" The reader soon realizes through Poe's jolting description of the narrator's state of mind that the protagonist has in fact descended into madness. The narrator claims that he loves the old man and has no motive for the murder other than growing dislike of a cloudy film over one of the old man's eyes. Poe effectively conveys panic in the narrator's voice, and the reader senses uneasiness and growing tension in the narrative. Through the first-person narrative of a madman, Poe effectively creates a gothic tale full of horror and psychological torment, a style he termed "arabesque."