Hi Aman,

As per the previous year trends and result anaylitics, if you get 20k rank in General category in jee main than your OBC category rank would b130+ marks in  around  AIR 5500.

Please note that this is an assumption based on previous year results, it might not be accurate but it will be somewhere are 5500.

Refer here for more info - JEE Main 2021 Exam - Admit Card (Feb 2nd Week), Dates, Syllabus, Pattern, Question Paper (careers360.com)

Feel free to ask doubts in the Comment Section.

I hope this information helps you.

Good Luck!