How many miracles does a person have to make to become a saint?

First of all, the saints do not perform miracles. The miracles are performed by God at the request of the saint.

Each individual case is based on its own merits. Usually 2 miracles are required, one for beatification and one for canonization. If the person died as a martyr, one or more miracles may be dropped. Other things can also be taken into consideration such as bilocation. incorruptibility, stigmata, heavenly perfume, etc.