Jee advanced cutoff scores changes every year as it depends on the no.of applicants and their scores

Pratik there is no certainty of marks in JEE Advanced examination for any category for getting admission in a good IIT because the mark vs rank criteria is totally relative depending on various factors like the number of students giving the exam, difficulty of paper etc. Hence it changes every year. Even after getting a rank there is no surety because the closing rank cut-off for each branch in each IIT changes every year.  

Still in if you want to play a little safer side in order to get admission in some branch in one of the old IITs then you need to aim for under 1000 rank in the OBC category and to get that rank it is always better to get a score above 180 marks.

Feel free to ask if you have any more queries. All the best!!