Hi

It is difficult to predict because marks vs rank keeps changing every year  depending upon various factors like

--------) number of students that appeared in the neet examination,

--------) kind of marks obtained by students  in neet

--------) toughness level of the neet examination etc

But yes,

>>>>>> With 636 marks ,

Your rank will be around 7824 - 9474 as per our predictor at

https://medicine.careers360.com/neet-rank-predictor?utm_source=qna&utm_medium=neet_rp

You hold very good chance for govt mbbs colleges under Tamilnadu state quota like Government K.A.P.V. Medical College, Trichy, Government Medical College, Omandurar Estate, Chennai etc

To get the complete list of colleges in which you have chances, you can go through our college predictor at

https://medicine.careers360.com/neet-college-predictor?icn=QnA&ici=qna_answer

With the help of predicted colleges you can make better choice while filling your choices of colleges during your counselling

To help in your counselling, we have mbbs companion in which in addition to college predictor tool you also get information regarding various counselling i. e all india , deemed, central and state  counselling and you get to attend live webinars with experts to guide you and get all your doubts cleared. The link is given below:-

https://www.careers360.com/mbbs-companion?utm_source=qna

Thank you