255/300 roughly converts to 85%. When I had appeared for JEE Main 2019, 85% meant around 306/360. With this much Score, subject to the difficulty of the paper and the competition one can be sure to secure a Rank within Top 1000, with percentile ranging anywhere around 99.9+. You should hence, focus on you JEE Advanced, and try to convert similar score there.

For more information about JEE Main do follow the link below

https://engineering.careers360.com/exams/jee-main

Hello Aspirant,

Since you have not mentioned your category so considering it is General.

If we go through the analysis of marks Vs Percentile Vs rank for JEE-Main 2020 then according to the marks mentioned by you in the question your rank and percentile is expected to be in the range of 210 - 103 and 99.9772051568448 - 99.9888196721667  respectively, you can check out marks Vs ranks Vs Percentile from the link given below :-

JEE Main 2021 Marks vs Percentile vs Rank – Calculate Marks using percentile score (careers360.com)

Or

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

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 2021/2022 then you can also check JEE-Main Learning package for your preparation

https://learn.careers360.com/jee-main-coaching/?icn=JEE_Main_knockout&ici=JEE_Main_article_view_sticky

I hope this information helps you.

Good Luck!!