However, to take any grad school course you must first have completed a bachelor’s degree. Specifically in your case you must also first be accepted to a computer science grad school program just to enroll to take those courses. This means you need to have a good GPA (3.0 minimum).

Therefore, without a bachelor’s degree you will need at least two more years of full time study just to get one, and possibly more, if not all your credits are accepted into a bachelor’s program. Then at least one year for grad school. So, 3 years full time studies minimum. However, you will probably want to finish the master’s program first since it’s a waste just to leave after one year (understand that it’s different than undergrad where you can pick your studies up later, often this is difficult if not impossible to do without having to start over). So considering 2 years for a typical master’s program duration, that’s 4 years more for you.