The minimum percentile required in JEE advanced to get an IIT college differs every year. I am providing you the cutoff for last year and from that you can make a assumption on what percentile you need to score.

                                               Minimum agaggregate 

Common Rank List(CRL) : 126

OBC NCL rank list : 114

SC rank list: 63

ST rank list : 63

So according to the category you belong to , you can check for the percentile and prepare likewise. But do remember that this is last year cutoff , so it may increase somehow so prepare accordingly 

Hello,

The authority of National Testing Agency (NTA) announces the requirements for qualifying JEE Advanced. This cut-off or eligibility qualifies you to IIT also. But beyond that you should have minimum percentage specified in Class 12 also. The requirement for qualifying JEE Advanced depends on your category also. For general it is ten percentile in every subject and thirty-five altogether. For others there will be minor deductions. Please visit https://engineering.careers360.com/articles/jee-advanced-cutoff for knowing cut-offs category-wise.