Can I do BCA without maths in 12th?

Yes, you can do BCA without Maths in class 12th as it is not a compulsory subject for BCA. If you look closely at the eligibility criteria of BCA, it is as follows 

• Candidates must have completed Class 12th in any stream from a recognized university with a minimum of 45-55% and also, with English as a subject (pass percentage varies from college to college).
• Candidates can also get admission on a merit basis, a written exam, or a personal interview. 
• Colleges also conduct entrance exams such as CUET, SET, IPU CET, etc. for BCA in India.

All in all, it can be safely concluded that Maths is not a compulsion for admission to the BCA program in most colleges. The eligibility criteria vary from college to college and thus are not true for every college.