As already answered the cut off marks for various and it is keep changing every year but there is perfectly at trend between the marks and I can assure you that in general above 180 marks for OBC is considered good and will fetch you some good and it is but for really good and it is and width of branches you must target for more than 220 so that at that mark you will be able to get any NIT but for branch is there maybe some compromise.

Hii

The cutoff keeps on changing every year depending on the level of difficulty of the paper, the number of students appearing in exams etc. So it is not possible to predict what will the exact cutoff be but yes to get into NITs you will have to keep a high target to be on a safe side. So prepare well and study smart and qualify your exam with a good score.
Refer to previous year cutoff to get an idea of the marks.
https://engineering.careers360.com/articles/jee-main-cutoff

Thanks!