Dear Arko, 

There is no such thing as Subject Wise Cutoff In JEE Main 2018. Candidates need not worry about passing eachsubject separately. They just need to score enough out of the total of 3 subjects together in admission in the IITs, NITs, IIITs, and GFTIs.

There will be JEE Main cut off to qualifying for JEE Advanced exam. Last year, JEE Main category wise cut off score (out of 360) was:

General- 81
OBC- 49
SC- 32
ST- 27
And candidates should have secured at least 75% marks in class 12th exam or be in the top 20 percentile in the class 12th exam conducted by the respective board. For SC/ ST candidates, the eligibility criteria is 65% marks in class XII.

I think it's helpful for you. 

Best wishes.