For the admission in IIT s you have to secure rank under 4-5 thousand accordingly rank may vary depending upon your choice and specific branch.

First of all you there are some eligibility criteria which you have to qualify for giving exam I.e.

1)

75% minimum marks in 12 th boards for general / obc category and for ST/SC it is 65% .

Or you are in top 20 percentile than also you are eligible.

2) year of passing 12 th must be same ; or previous ; or  previous from previous one

Than the procedure to get admitted :

Firstly you have to qualify JEE mains exam 

( Which is held twice in a year Jan and in April.

You have to qualify in any one of two chance.

Registration of JEE mains started after August for January chance and after February for April exam)

After that you have to register for JEE advanced .

And exam will held in may.( You have to qualify in each of the subjects with overall good rank in JEE advanced).

One thing JEE mains and advanced results and ranking are both separately .

And depending upon your choice and branch you can check last year's cut offs.

And your rank will decide that will you get seat in particular college or not .

Because according to the exam difficulty level and number of candidates rank vary every year on same score.

So if exam will be easy / normal 

Than you should score atleast 70 % marks to be in safe position and if it is of hard level than you should score atleast 60%marks.

Prepare yourself very hard and with proper guidance so that you can handle both the situation.

So good luck