Comment Ratio (CR) is simply the ratio of the line of comments to the total number of lines of code. A good comment ratio makes the code easier to understand, maintain and expand. If the comment ratio is too low, the file will be hard to maintain. A new developer will struggle to understand such a file. If CR is too high, the file is more appropriately a document rather than a source code file. If CR is too high, it may also mean that the implementation/ structure/naming is unintuitive.