Hello,
To get admission in top engineering colleges(IITs,NITs,IIITs,BITS) you need to score minimum 75% marks in your 12th boards.But to get average colleges like sate level colleges and private colleges you need to score 60% in your 12th boards.
In some state engineering colleges(JEECE,COMEDK) only 45% minimum is required in 12th.
Good luck.