Dear Bikash,

It is difficult to predict the cut off marks for CSE branch in NITs and IITs. 

NITs cut off marks for CSE varies. To get admission in NITs you should score more then 130 marks in JEE Main in general category other state quota. 

To get CSE branch in top NITs you should try to score more then 230 marks in JEE Main exam in general category other state quota.

JEE Advanced maximum marks are not defined :

Maximum Marks vary every year like below:

2017- 366

2016- 372

2015 - 504

2014 - 360

So, it is difficult to predict marks as exam pattern and marks change every year but you should score more than 50% marks to get good branch in Top IITs.

Good Luck!!