In order to get eligible to attend the wbjee you just need to cross your category cutoff however this will not ensure your admission. The rank required to get admission varies among colleges and also depends upon your branch. You can check previous year closing rank to get the rough estimation. Please go through the link given below.

https://engineering.careers360.com/articles/wbjee-cutoff/amp#referrer=https://www.google.com

Thank you.

Hope it helps.