What is considered a good or bad percentage of similar content?

While each case is unique, there are a few variables to keep in mind. The amount of content you have uploaded is a large factor, for example a document of 250 words is very different from a 10,000 word document. This can alter the percentage of similar content from a very small to a larger number. This is why you can view the similar passages that are highlighted easily to decide if there is legitimate plagiarism. If you are a student, there is typically a percentage of similar content you must stay under. Many teachers have a range of 20-30%, so this is a good bar to set when you receive your results.