Hello Vivek,

Eligibility criteria for admission into IIM Calcutta is a student must have obtained a minimum of 50% or equivalent CGPA in bachelor's degree or 45% for other categories. The candidates will then be shortlisted on the basis of the CAT cut off and for only those students past academic results will be assessed. In this according to your marks you will get 10 points for class 10 and 0 for class 12. However if you obtain 100 percentile there are chances that you will still have overall points more than other candidates which can get you admission in the college. 

For further information please refer to the following careers360 link. 

https://www.google.com/amp/s/bschool.careers360.com/articles/iim-calcutta-admission-criteria/amp

Hope this information was helpful.

Good luck !