How big do event horizons get?

Answer 1

Assuming you mean the event horizon of a black hole (there are other types as well), the diameter of a black hole as measured by its event horizon is directly proportional to its mass. The larger the mass, the larger the diameter. Thus, as a black hole's mass increases, it will get bigger. The only limitation is how much mass a black hole is able to incorporate from its surroundings.

Answer 2

The size of an event horizon is directly related to the mass of the object it surrounds. For example, the event horizon of a solar mass black hole is roughly 3 kilometers in radius. The event horizon of supermassive black holes at the centers of galaxies can be millions to billions of kilometers in radius.

Answer 3

it depends on the size of the black hole. the larger the black hole, the farther the event horizon will be from the start of the black hole.