Here is an infographic for the new formula for IIT JEE. Please check out the related post for full description.
Note: Percentile is not same as percentage. Percentile score is calculated out of 100 and is the percentage of people who have scored less than you in the exam. For example, if there are 100 students, and your rank is 3, that means there are 97 students that scored less than you – means you are 97 percentile.
Your percentile can be higher that 80 even if your percentage is less than 80.