BIT Mesra NIT Sindri take admission from JEE score /percentile and do not look into your board percentage/score but they do demand a minimum 12th percentage marks that being 75% for general category and 5% for SC/ST. The candidates must have secured at least 75% marks or be in the top 20 percentile in the 12th Class Examination conducted by respective boards. For SC/ST students, there shall be a relaxation of 5% in this criterion.

So you just need to score good in jee mains and secure minimum board percentage to get into bit mesra. Best of luck