Hello Nisha, 

There are a number of courses offered in IIT Madras. Since you have not mentioned about the course I am mentioning the eligibility criteria of all those courses offered in IIT Madras.

1. B.Tech: entrance exam is JEE Main and JEE advance. Applicants should have passed higher senior secondary with a minimum of 75% marks to be eligible for the exam. However it will not play any role in determining your rank in JEE Mains.

2. Integrated M.A.: Entrance exam is HSEE. All applicants should have passed 10+2 with a minimum of 55% aggregate. 

3. M.Tech.: Entrance exam is GATE. Although 10+2 marks are not asked for eligibility but a minimum of 60% marks in bachelor's degree is mandatory for all general candidates, whereas a relaxation of 5% is given for all SC/ST/PH candidates.

4. M.Sc.: admission done on the basis of JAM score. Like M.tech, only bachelor's degree with a minimum of 55% aggregate marks is essential for being eligible.

Therefore depending on the course you are applying for 10+2 marks maybe needed.

Hope this information was helpful.

Good luck!