How many editing passes will my novel need?

 Consider an editor’s accuracy rate.
Most edited documents will have a 90% accuracy rate, meaning that for every 100 errors found, 10 of them have slipped through, uncaught. Take into consideration a 50,000-word novel. If an editor finds 5,000 errors on the first pass, that means at least 500 remain.
So if on the second pass 500 errors are found, then at least 50 will remain. After the third pass, approximately 5 errors will remain.
An author should have their novel edited until they are happy with the possible remaining number of errors.
Say your line edit yields 4,000 revisions. I recommend a second line edit pass, which may yield roughly 400 revisions. I would then recommend a copy edit. You may have more copy edits than the second line edit pass because the editor is looking at your sentences differently. The first pass might have 1100. A second line edit pass might yield 110 revisions. I would recommend a proofreading pass then, and depending of the number of revisions noted, I might recommend a second proofreading pass. That will usually find most of the remaining errors.
But that’s six edits, you say. Yes.
Emrys Pumpkin Press does a comprehensive edit—line, copy, and proofread all in one. (If we change the structure and grammar of a sentence, we will make sure punctuation is correct as well.)An example of revisions we might find in a 50,000-word novel.
First pass (5,000) Second pass (500) Third pass (50) Fourth pass (5)
That’s four passes. Better than six passes.
Remember. Editing styles differ from one editor to the next. One editor might be better at pointing out one type of revision than another editor. Editors may differ on comma placement. I often hear authors say, “My last editor didn’t find this many errors” or “My last editor didn’t flag that.” Different editors, different style guides, different emphasis. An author must take all these into consideration. Sometimes it pays to submit the same ten pages for a free edit to several editors to find the one whose editing style you prefer the best.
So what’s the answer to the question, how many editing passes will my novel need? As many as it takes, until you, the author, are happy with the possible remaining number of errors.