My essay got 1% similarity in Turnitin, but my professor still says it’s plagiarism. What should I do?

I think there is possibly more to this situation that you’re saying? Why does the professor think your paper is plagiarized? On what grounds? It obviously isn’t Turnitin. Perhaps there is another reason? Maybe a direct comparison to an outside source the professor made on their own?

Turnitin isn’t a legal accusation or a science. All it does is provide an indication for an instructor to to look more closely. A 100% similarity report isn’t guaranteed proof of plagiarism. On the other end, a 1% similarity isn’t proof of an absence of plagiarism. After all, if you plagiarized from a source that Turnitin doesn’t have access to—like a hard copy book or something in the course materials—it naturally wouldn’t show up.

So, I’d advise being honest with yourself—did you copy work from some other place and present it as your own? You know if you did or not. If you did and the professor has outside proof of it, your best bet is to come clean and own up. Otherwise, you’ll just be proving yourself a liar (and not a very good one at that) in addition to a cheat.

That said, if you really wrote the whole thing yourself, politely ask to see to evidence against you. Provide proof like document version histories that show where and how you wrote the paper. Be respectful. 90% chance that you can work it out with the professor and it can even possibly end on a positive note. In the 10% chance that you have one of those lazy or crazy professors out there who is just being a jerk, then, and only then, escalate it to the chair, and be ready to politely provide all of this proof up front.