Hiii...

Just after 12th

the total CA course duration after 12th can be estimated to be 4.5 years. The only challenge is that you have to complete all its levels in your first attempt. Because each number of attempt increases your six months in this journey. 

CA after graduation..

the total duration to complete the CA course duration after graduation is 3 years approx. Although 3 Years is the minimum duration, every attempt increases your six months.

Hope you get it...