I agree with
LittleMoW, less so with
speedilly. If you're the type of person who would fit at Harvard, you're going to be able to make an executive decision about what's the right length to tell
your story effectively. Conforming to some "standard" isn't ultimately going to help you succeed.
That said, having a fresh set of eyes read your essay, preferably someone you trust to give you honest feedback, would be helpful. It seems like if you're asking for advice, you're somewhat unsure about the length and possibly about the content. I can tell you that my finished essay is around 1100-1200 words, and I am more than confident that it tells my story effectively (but I can't say I felt that way several drafts ago). If I don't get in, I
know it won't be because of my essay. You should feel the same way when you hit that submit button.