Jay, you haven't mentioned your Category. Neverthless, in 2018 under State Quota, the cut offs for various Categories have been as follows:
General Category: 370
Now this is 2018 data and we do not have 2019 data yet. But i 2019, the individual cut offs on an average increased by 60-75 marks. So if you want to secure a seat in Tamilnadu, you need to aim for atleast 200-250 marks more than mentioned against your Category here. Now, cut offs change every year and are dependant on various factors such as no.of Candidates appearing for the exam, no,of Candidates qualified, top NEET score and difficulty of the exam. For any guidance during counselling and admission, you can use our MBBS Companion: https://www.careers360.com/mbbs-companion
You didn't mention the category. So I will answer supposing you belong to general category. The cut off solely depends on hardness of question paper. But you can take a rough estimation of 505-515. It is based on previous year figures.