There is no rule for exactly how long an introduction should be. You must consider the length of your overall paper when writing your introduction. An appropriate length for a five-page essay is about half a page, but if you are writing a 40-page paper, your introduction will span several pages and multiple paragraphs.Basically, think of it as essay writing reviews 5 paragraphs of approximately 100 words each. That’s approximately 6 or 7 sentences depending on how long you make them. Here are the 5 paragraphs for your 500 word essay: The introduction.