Are you asking for JEE Main Entrance Exam eligibility? Then there is no any marks eligibility but in Order to appear in IITs, NITs, IIITs, GFTIs you should have minimum 75% in class 12th as a general category & 65% as a reserved category or you should be in top 20 percentile in your class 12th exam conducted by the respective board. You can check the further eligibility with the given below link.

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

Good Luck!