Dear Student,

In order to take admission in IITs you have to appear for JEE Advanced exam.

To be eligible for JEE Advanced you have to qualify for JEE Main exam first. 

To get admission in IITs you should have 75% marks in your board exam or you should be in top 20 percentile for general category and 65% for SC/ST. 

To check the cut off rank you can refer below link

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

Good Luck!!