Some require twenty hours, other requires forty hours, and yet others, require a minimum of two hundred and fifty hours. The average amount of time it takes a pilot to get their private pilot license is about six months, during which time they acquire all the knowledge and experience, take tests, and fly a lot with their
instructor and alone.
I would suggest you to read lot of manuals, forums and do your self study. There are many online resources like
http://www.privatepilotssecrets.com which will give you free e-courses to know all about flying.
More Important is Have fun and enjoy your flying.