dear aspirant;

Firstly,i would tell you about the JEE advanced because it creates the main difference.

For general category,around 50 % marks will get you some decent branch .

If you want to take CSE in old IIT’s you should score around 70 % marks.

For electrical,ECE and other top branches,60% will be good enough.

And if you want to get into a decent IIT with a decent branch,you should score atleast 50%.

Suppose if you don’t get a very good rank and you are not getting a good branch in an IIT,you can take whatever the branch you are getting and study hard during the first year of college to get a department change .Department change is a way to change your department based on your outstanding academic performance.

But department change is risky.I would suggest you to study hard during JEE preperation.

I don’t know much about the present system for board marks but even if it’s top 20 percentile,85 % in boards will make you eligible for JEE advanced.And JEE mains is quite easy to qualify . Around 120 marks in mains is sufficient to qualify for advanced.

Thank you.

Based on you your JEE mains score you can not get admission in IIT, for getting admission in IIT you will have to appear in JEE Advanced and have to clear it with a good mark.

Based on you your JEE mains score you can get admission in NITs and IITs.

All the very best and good luck.