Hi, Akhilesh.

your 305 marks out of 500 would make 61% in your class 12th. Assuming you have done your 12th in PCM.

If you want to get admission into IIT your minimum score in 12th (for general category) has to be 75% and 65% for reserved categories (or top 20 percentile of your high school qualifying exams).

I am attaching a link for more information on this;

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

hope it helps,

good day!