Hey, 

For being eligible to write BITSAT, candidates must have passed 12th or equivalent exam from any recognized board with Physics, Chemistry, Mathematics and English Subjects. Candidates must have obtained 75% marks in PCB or PCM group with at least 60% in each subject physics, chemistry, mathematics/biology.

If you have 60% in each subject, you'd be eligible to write the exam. 

Hope this helped you 

Thank you and keep asking :)