Hello Anku,
'Top 20 percentile' in any exam means that you are among the top 20% of all the students who appeared in that exam and other 80% are below you...
Mathematically, percentile= number of student below you/number of students who appeared in the exam....
Hope this helps...

It is for IITs, NITs, IIITs and GFTIs.

Hello there. So let's start by understanding what percentile actually is. Percentile is a sort of percentage that is being calculated by keeping the topper in reference. When we calculate percentage we divide by total marks while in case of percentile we divide by the number gained by topper.

So as for 20 percentile system, it means that the students having top 20 % with respect to topper. And yes this system is in IIT only. But their is also another condition for IIT which is that you should have scored at least 75% in +2