Hello Aspirant,

See there is no any exact formula to calculate category rank from CRL rank because it might differs depending upon various factors like number of total candidates, total candidates from OBC category and so on. But If we go through the analysis of CRL Vs OBC ranking for JEE-Main 2020 then according to the CRL rank mentioned by you in the question your OBC rank is expected to be in the range of  5000-6000, you can also check out marks Vs ranks Vs Percentile from the link given below :-

https://engineering.careers360.com/articles/jee-main-marks-vs-percentile

Or

You can also use JEE-Main Rank Predictor to predict your rank :-

Note that the rank which is predicted is only the expected rank on the basis of previous year's data so your actual rank might vary depending upon current factors. To give you an idea of your approximate rank we have provided the expected range of rank.

On such rank you have good chances for different NITs and IIITs. To have a list of all those colleges which you can get based upon your marks, category, and state you can use JEE-Main College Predictor:-

https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer

If you are preparing for JEE-Main 2021 or 2022 then I would recommend you to check the resources made by our experts to help aspirants like you in the best and smart preparation of JEE-Main 2021 or 2022 :-

https://learn.careers360.com/jee-main-coaching/?utm_source=%20QnA

I hope this information helps you.

Good Luck!!