Typically, it takes approximately 45 minutes to proofread 500 words. This assumes you are taking your time to do an thorough job and not just quickly skimming over the words. The exact length of time will vary depending on your reading speed and the complexity of the text you are proofreading. Additionally, the time it takes to proofread 500 words will be greatly influenced by the level of detail and accuracy that is expected. A basic proofread to catch spelling and grammar errors or typos may take substantially less time than a more comprehensive job which requires you to parse the language for its accuracy and meaning.
That said, it is always wise to give yourself a buffer of some kind when proofreading; this will help to ensure that you can properly review and edit the text without feeling rushed.
