Usually you should consider your top five subjects' scores but the percentage criteria varies from university to university and from course to course.

Can you please tell me you are asking for which exam?

For JEE Main it is mandatory for candidates to have taken 5 subjects in 12th or qualifying exam

The 5 subjects for B.Tech/ B.E. are:

1-Language
2-Physics
3-Mathematics
4-Any one of (Chemistry, Biology, Biotechnology, Technical Vocational Subject)
5-Any other subject

Good Luck!!