Hello Mrinal

81.88 percentile is not that bad but yes it can help you in getting Nit's being a ST category. Cutoff's are still not out but you can calculate your rank by sing one simple formula suppose 874469 are the number of candidates appeared for the January exam. So rank formula is (100- your total score) * 874469 / 100. This will give you the approx rank and hence you can relate with the previous years cutoffs including category rank wise.