Its a question of non trade people, generally non technical or unskilled people use to ask such questions (its Ok for student to ask such question because the exposure to designing of concrete might not be a much powerful enough to clear concept at your collage).
I am considering you are a first or 2nd year student of engineering.
Concrete mix design is a rt which is widely used now a days everywhere, and the art of using stated values in proportions for each grade is become a waste of money and uncertainty of strength, which makes owner sleepless.
In past or even in Today's time where a Engineer who do not understand designing or at a Project of small homes and in case of non technical people who leads the Project, a conventional method of proportion is used to determine the concrete materials and quantity, which most of the time fails to provide you authentic and accurate data.
So basically understand, get involve in concrete mix designing and learn that art.
once you understood it, you will be able to find everything you are questing for.
Every design have different parameters and according to parameters one can determine the quantities.
hope you understood my point of view.
You can learn more about concrete mix designing by reading articles from below section.