How do I Calculate aggregate marks of class 12 for JEE Main 2020

How do I calculate aggregate marks for JEE Main 2020? I saw that there is a compulsory subject combination of Physics , Mathematics and Either of (Chemistry, Biology, Biotechnology,Computer Science etc.) So how am I supposed to calculate my aggregate

Just 75 percent is required to fill jee main and for Advanced you need atleast 80% in boards

no only 75% required for writing advanced exam or top 20 percentile...no criteria in jee mains @abhijit_2020

I think he is talking about taking admission in iit/nit/IIIT/cfti system where minimum 75% is required.