Hii Ravi!
There's no such time to count. It totally depends on what do you want to do and how much time you take. After 12th, you need to give CLAT entrance examination and get admission in a law college. You can either opt for 3 years course or 5 years integrated course, which is better. Then, you can either study further, do your masters and PhD in a particular field or you may start practicing in courts under senior advocates and learn, gain experience and get promoted gradually. You can even clear exams conducted by Public Service Commission and become a judge. So you see, it's more than 5 years for sure....but there's no end. Hope this helps.
Good luck!