How much should I charge as a private tutor

It depends, the going rate for a professional tutor in my area is around £20 per hour. But in London, for example it could be around £30+ per hour. If you are just doing it as you know about the subject I would expect to charge a lot less than a professional and if it is for a friend, or someone you know then that would be about right. I know someone who tutors people he knows at GCSE level for £8 per hour. Hope that helps