How much would a professor's recommendation letter help?

I am getting a recommendation letter from the professor of the school that I am applying to( ranked 15). How much of a difference would this make if my gpa and sat is in the range?

earlier you posted

So this parent will lean on one of their pals to write a letter on your behalf. How much will it help? Little if any, and has the potential to hurt a lot. I know a guy at a top-10 tech company that is always getting pestered by relatives to write letters of recs for their kids. These are relatives he barely knows but when they find out he works at X all of a sudden he’s their close kin. So he provides them the letter, usually prompting them to write it for him and he’ll sign it. Why not, he doesn’t actually know any of the kids “accomplishments”. Then, having satisfied the relatives he sends an email to HR letting them know the circumstances of the letter. I wonder what will happen if your situation is similar?

Did you work under this prof’s tutelage? You did research under him/her? If not, then it’s less than worthless. It actually HURTS you. You water down your app package with a clearly meaningless rec letter and shows you have poor discernment.

The rec letter is about the subject, not the writer. A enthusiastic 1st year teacher’s authentic rec letter for you is 8,000x better than this prof’s diaphanous rec letter.