The exact cutoff percentile for qualifying JEE Mains and to be eligible to give JEE Advance is not yet announced by National Testing Agency (NTA). 

Since JEE Mains is again going to be conducted in April it cannot be estimated precisely but it is predicted that students with above 85 percentile will be eligible to give JEE Advance.

To be sure about it I suggest you to wait for the officials to announce it. 

If you still have any queries feel free to ask in the comment section down below.