The cutoff for colleges in Kolkata is quite high. With 85-90%, you should get into good colleges under Calcutta University. But here are some things that you should keep in mind.

• As the number of students applying is way more than the number of colleges, chances are you won’t get selected through the first or second round. 
• The colleges release multiple counseling lists. So, you need to wait. As many students withdraw their admission, leaving seats vacant.
• If you aren’t confident about getting admission, apply to as many colleges as you can to keep your options open.
• You can always take admission at a college you are easily getting into and withdraw when you get selected in your preferred college.

Also, you always have the option to get admission into private universities.