Hello aspirant...
What you want to ask ,it is not clear from your question.
Candidates will have to score a minimum of 75% (for SC/ST it is 65%) in their class 12th or be in the top 20 percentile of their respective boards to be considered for admissions in NITs,IITs.
Many other college also make.it mandatory to score 75 percernt marks in 12 th board.
But there are various engineering entrance exam in which you can apply for admission .
Hope it helps you.
All the best.

Hello Piyush
As mostly all the colleges give admission on basis of jee mains for the admission through josaa you have to secure atleast 75 %marks.
But there are some colleges which consider the jee mains ranking but conduct their own counseling and they have 65% criteria.
And some college have their own entrance and percentage criteria.
You can go in state college which have low minimum criteria.
You can go in private colleges but in which college you want to go check the eligibility criteria for that.
Good luck.

Hello dear, 

If you are scoring below 75 percent marks in your Higher secondary School  examination conducted by the respective boards and you are not in top 20 percentile, then you are loosing opportunity to take admission in prestigious institutions of India. You will not allow to take admission any iits and nits .

Hope this information helps you. 

Good luck