minimum marks in class 12th bihar board to qualify for iit?
In case, you are asking for top 20 percentile then kindly check the below detail of previous year -
Bihar Intermediate Education Council -
General - 315
OBC-NCL - 308
SC - 297
ST - 300
PwD - 297
For reference, you can go through the below link -
https://josaa.nic.in/webinfocms/Handler/FileHandler.ashx?i=File&ii=87&iii=Y
Good Luck!!!