Dear Aparna,

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 40 to 45% marks to get good branch in Top IITs.

To check the cut off rank you can refer below link

https://engineering.careers360.com/articles/jee-advanced-cutoff

Good Luck!!